OK, I've tried to update Sam's original post with players from the UK (plus some other off the top of my head) as that is who I'm most familiar with, will try to add players elsewhere around the world later. All I really have to go off is this thread and Wikipedia some could be wrong. For now this is only senior players, if you know of some youngsters I'll add them in. Also, I've only added players from Conference level and above. Bold means they've been capped at some level.
Antigua & BarbudaMoses Ashikodi - F - Kettering/England (also Nigeria)
Dexter Blackstock - F - Nottingham Forest/England (also Jamaica)
Anton Blackwood - D - St. Albans City/England (also Jamaica)
Justin Cochrane - M/D - Boreham Wood/England
Kiernan Hughes-Mason - F - Kettering/England
Nathaniel Jarvis - F - Cardiff City/Wales
Marc Joseph - D - Altrincham/England
Mikele Leigertwood - M - Reading/England
Marvin McCoy - D - Wycombe Wanderers/England
Kieran Murtagh - M - Cambridge United/England
Josh Parker - D - Oldham/England
Myles Weston - M - Brentford/England
Ineligible:
Kieron Dyer - M - West Ham United/England (played for England)
Colin Kazim-Richards - M - Galatasaray/Turkey (played for Turkey)
Ledley King - D - Tottenham/England (played for England)
BarbadosNick Blackman - F - Blackburn Rovers/England (also Holland and Poland)
Emmerson Boyce - D - Wigan Athletic/England
Jonathan Forte - M - Southampton/England
Fitz Hall - M - Queens Park Rangers/England
Marlon Harewood - F - Nottingham Forest/England
Paul Ifill - M - Wellington Phoenix/Australia
Thomas Ince - M - Blackpool/England
Dean Leacock - D - Leyton Orient/England
Nicky Maynard - F - Bristol City/England (also Guyana)
Mark McCammon - F - Braintree/England
Lewis Montrose - D - Wycombe/England
Jon Nurse - F - Dagenham and Redbridge/England (also Guyana)
James Perch - D - Newcastle/England
Alvin Rouse - G - Longford Town/Ireland
Louis Soares - M - Hayes and Yeading/England
Tom Soares - M - Stoke City/England
Ineligible:
Ashley Cole - D - Chelsea/England (played for England)
Danny Gabbidon - D - QPR/England (played for Wales) (also Jamaica)
Anthony Straker - D - Aldershot/England (played for Grenada)
BermudaReggie Lambe - M - Ipswich Town/England
Freddy Hall - G - Northampton/England
Nahki Wells - F - Bradford/England
Cayman IslandsTuda Murphy - G - Portadown/Northern Ireland
Tristan Plummer - F - Portimonense/Portugal (also Jamaica)
Jamie Wood - F - The New Saints/Wales
Ineligible:
Barry Hayles - F - Truro City/England (played for Jamaica)
CuraçaoShelton Martis - D - Doncaster Rovers/England
DominicaKieran Agard - F - Yeovil/England
Anthony Edgar - M - West Ham/England
Jay Emmanuel-Thomas - M - Ipswich/England (also Saint Lucia)
Jefferson Louis - F - Gainsborough Trinity/England
Richard Pacquette - F - Eastbourne/England
Ineligible:
Jermain Defoe - F - Tottenham/England (played for England)
Dominican RepublicNathan Ellington - F - Watford/England (also Jamaica) (could be Dominica instead)
French GuianaMarc-Antoine Fortuné - F - Celtic/Scotland
Florent Malouda - M - Chelsea/England
Jason Roberts - F - Blackburn Rovers/England
GrenadaJermaine Beckford - F - Leicester/England (also Jamaica)
Bradley Bubb - F - Aldershot/England
Delroy Facey - F - Hereford/England (also Jamaica and Trinidad and Tobago)
Cameron Jerome - F - Stoke City/England
Leon Johnson - D - Wycombe Wanderers/England
Sharlie Joseph - M - New England/USA
Dwane Lee - M - Hayes and Yeading/England
Courtney Pitt - M - Cambridge United/England
Jason Roberts - F - Reading/England
Craig Rocastle - M - Kansas City Wizards/USA
Anthony Straker - D - Aldershot/England
Bradley Wright-Phillips - F - Charlton/England (also Jamaica)
Ineligible:
Jaime Peters - M - Ipswich Town/England (played for Canada)
Shaun Wright-Phillips - M - Manchester City/England (played for England)
GuadeloupeMickaël Antoine-Curier - F - Ermis Aradippou/Cyprus
Pascal Chimbonda - D - QPR/England
Jean-François Christophe - M - Southend United/England
Miguel Comminges - D - Southend/England
Sylvain Distin - D - Everton/England
William Gallas - D -Tottenham/England
Willy Guéret - G - Kettering/England
Therry Racon - M - Millwall/England
Louis Saha - F - Everton/England
Ronald Zubar - D - Wolves/England
Stéphane Zubar - D - Plymouth/England
GuyanaJay Bothroyd - F - Cardiff City/England (also Jamaica)
Titus Bramble - D - Wigan Athletic/England
Matthew Briggs - D - Fulham/England
Carl Cort - F - Brentford/England
Leon Cort - D - Burnley/England
Fabian Delph - M - Aston Villa/England
Nicky Maynard - F - Bristol City/England (also Barbados)
Ricky Shakes - M - Ebbsfleet/England (switched after being capped for Trinidad and Tobago, but only in a friendly)
Jerome Thomas - M - West Brom/England
Ineligible:
Jon Nurse - F - Dagenham and Redbridge (played for Barbados)
HaitiJean-Francois Lescinel - M - Sheffield United/England
JamaicaTroy Archibald-Henville - D - Exeter City/England (also Saint Vincent and the Grenadines)
Kieran Agard - F - Yeovil/England
Cliff Akurang - F - Chelmsford/England (also Ghana)
Michail Antonio - M - Reading/England
Giles Barnes - M - Derby County/England
Leon Barnett - D - Norwich/England
Kyle Bartley - D - Arsenal/England
Marcus Bean - M - Brentford/England
Jermaine Beckford - F - Leicester/England (also Grenada)
Marcus Bent - F - Middlesbrough/England (on loan from Birmingham)
Dexter Blackstock - F - Nottingham Forest/England (also Antigua and Barbuda)
Anton Blackwood - D - Tottenham/England (also Antigua and Barbuda)
Jay Bothroyd - F - Cardiff City/England (also Guyana)
Deon Burton - F - Gabala/Azerbaijan
Darren Byfield - F - Walsall/England**
Danny Cadamarteri - F - Huddersfield/England
Jamal Campbell-Ryce - M - Bristol City/England
Omar Daley - M - Motherwell/Scotland
Claude Davis - D - Crawley Town/England (on loan from Crystal Palace)
Chris Dickson - F - Bristol City/England (on loan from Charlton) (played for Ghana but only in two friendlies)
Kieran Djilali - M - Crystal Palace/England
Craig Dobson - M - Mansfield/England
Clayton Donaldson - F - Crewe/England
Lloyd Doyley - D - Watford/England
Lloyd Dyer - M - Leicester City/England (also Montserrat)
Nathan Dyer - M - Swansea/England (maybe another as well)
Nathan Ellington - F - Preston/England (also Dominican Republic)
Marvin Elliott - M - Bristol City/England
Jason Euell - F - Blackpool/England**
Craig Fagan - M - Hull City/England
Liam Feeney - M - Bournemouth/England
Simon Ford - D - Chesterfield/England
Ricardo Fuller - F - Stoke City/England
Anthony Gardner - D - Crystal Palace/England
Ricardo Gardner - D - Bolton/England
Joel Grant - M - Crewe/England (only capped at underage level)
Ian Goodison - D - Tranmere/England
Barry Hayles - F - Truro City/England
Danny Haynes - F - Bristol City/England
Reuben Hazell - D - Oldham/England
Michael Hector - D - Reading/England
Karl Henry - M - Wolves/England
Zavon Hines - F - Burnley/England
Junior Hoilett - F - Blackburn Rovers/England
Dean Howell - D - Crawley Town/England
Luke Hubbins - M - Birmingham/England
Chris Humphrey - M - Motherwell/Scotland
Ben Hutchinson - F - Lincoln City/England (on loan from Celtic)
Jermaine Johnson - M - Sheffield Wednesday/England
Marlon King - F - Birmingham/England
Richard Langley - M - Pattaya United/Thailand
Kevin Lisbie - F - Colchester/England**
Mark Little - D - Peterborough/England
Adrian Mariappa - D - Watford/England (also Fiji)
Mark Marshall - M - Barnet/England
Jobi McAnuff - M - Reading/England
Garath McCleary - M - Nottingham Forest/England
Lewis McGugan - M - Nottingham Forest/England
Leon McKenzie - F - Northampton Town/England
Aaron McLean - F - Hull City/England
Anthony McNamee - M - Woking/England
Tyrone Mears - D - Burnley/England**
Marcus Milner - M - Southend/England
Darren Moore - D - Barnsley/England
Ravel Morrison - M - Manchester United/England
Jennison Myrie-Williams - F - Dundee United/Scotland (not sure on this one)
Isaac Osbourne - M - Aberdeen/England
Isaiah Osbourne - M - Hibernian/England
Liam Palmer - M - Sheffield Wednesday/England (also Scotland)
Jermaine Pennant - M - Sunderland/England
Darren Pratley - M - Swansea City/England
Tristan Plummer - F - Portimonense/Portugal (also Cayman Islands)
Nyron Nosworthy - D - Watford/England
Dennis Oli - M - Gillingham/England
Nile Ranger - F - Newcastle United/England
Nathan Redmond - M - Birmingham/England
Michael Ricketts - F - Tranmere/England (capped by England but I think in a friendly)
Theo Robinson - F - Derby County/England
Ricky Sappleton - F - Macclesfield/England (only capped at underage level)
Damian Scannell - M - Dagenham and Redbridge/England (also Ireland, hands off!)
Sean Scannell - M - Crystal Palace/England (also Ireland, hands off!)
Danny Simpson - D - Newcastle United/England
Frank Sinclair - D - Wrexham/England
Scott Sinclair - M - Swansea/England
Nathan Smith - D - Chesterfield/England
Darren Stephenson - F - Bradford City/England
Damion Stewart - D - Bristol City/England
Daniel Sturridge - F - Chelsea/England
Cleveland Taylor - M - Burton/England (only capped at underage level)
Sanchez Watt - F - Arsenal/England
Marvin Williams - M - Torquay United/England
Lee Williamson - M - Sheffield United/England
Bradley Wright-Phillips - F - Charlton/England (also Grenada)
Lewis Young - F - Burton/England (on loan to Hereford)
Ineligible:
Darren Bent - F - Aston Villa/England (played for England)
Sol Campbell - D - Arsenal/England (played for England)
Delroy Facey - F - Lincoln City/England (played for Grenada) (also Trinidad and Tobago)
Danny Gabbidon - D - West Ham/England (played for Wales) (also Barbados)
Simeon Jackson - F - Gillingham/England (played for Canada)
David James - G - Portsmouth/England (played for England)
Aaron Lennon - M - Tottenham/England (played for England) (also Ireland)
Clinton Morrison - F - Sheffield Wednesday/England (played for Ireland)
Darius Vassell - F - Ankaragücü/Turkey (played for England)
Shaun Wright-Phillips - M - Manchester City/England (played for England)
Ashley Young - M - Aston Villa/England (played for England)
MartiniqueNicolas Anelka - F - Chelsea/England
Frédéric Piquionne - F - West Ham/England
MontserratTitus Bramble - D - Sunderland/England
Michael Duberry - D - Oxford United/England
Lloyd Dyer - M - Leicester City/England (also Jamaica)
Anthony Griffith - M - Port Vale/England
Izak Reid - M - Morecambe/England
Saint Kitts and NevisNathan Abbey - G - Rushden and Diamonds/England
Matthew Berkeley - M - Hyde/England (capped only at underage level)
Jordan Bowery - F - Chesterfield/England
Aaron Lescott - D - Bristol Rovers/England
Adam Newton - D - Luton Town/England
Calum Willock - F - Ebbsfleet/England
Ineligible:
Joleon Lescott - D - Manchester City/England (played for England)
Micah Richards - D - Manchester City/England (played for England)
Saint LuciaJay Emmanuel-Thomas - M - Ipswich/England (also Dominica)
Anton Ferdinand - D - Sunderland/England
Jerel Ifil - D - Kettering/England (also Cyprus)
Philip Ifil - D - Kettering/England (also Cyprus)
Junior Stanislas - M - Burnley/England
Ineligible:
Justin Cochrane - M - Hayes and Yeading/England (played for Antigua and Barbuda)
Jermain Defoe - F - Tottenham Hotspur/England (played for England)
Rio Ferdinand - D - Manchester United/England (played for England)
Jason Roberts - F - Blackburn Rovers/England (played for Grenada)
Saint Vincent and the GrenadinesNathan Abbey - G - Rushden and Diamonds/England
Kieran Agard - F - Yeovil/England
Troy Archibald-Henville - D - Exeter City/England (also Jamaica)
Theo Lewis - F - Cheltenham Town/England
SurinameMark de Vries - F - Cambuur Leeuwarden/Netherlands
Royston Drenthe - M - Real Madrid/Spain
Marvin Emnes - F - Middlesbrough/England
Gianni Zuiverloon - D - West Brom/England
(many more in Europe)
Ineligible:
Mario Melchiot - D - Wigan Athletic/England (played for Netherlands)
Trinidad and TobagoMarvin Andrews - D - Wrexham/Enland
Kevin Austin - D - Chesterfield/England**
André Boucaud - D - Kettering/England
Gavin Hoyte - D - Brighton/England (on loan from Arsenal)
Justin Hoyte - D - Middlesbrough/England
Carlos Edwards - M - Ipswich Town/England
Kenwyne Jones - F - Sunderland/England
Collin Samuel - F - Saint Johnstone/Scotland
Jlloyd Samuel - D - Bolton/England
Jason Scotland - F - Wigan/England
Ricky Shakes - M - Ebbsfleet/England (switched to Guyana)
Silvio Spann - M - Wrexham/England
Jake Thomson - D - Kettering/England
James Vaughan - F - Everton/England
Tony Warner - G - Hull City/England
Bobby Zamora - F - Fulham/England
Ineligible:
Delroy Facey - F - Lincoln City/England (played for Grenada) (also Jamaica)
Clinton Morrison - F - Sheffield Wednesday/England (played for Ireland)
Unknown (but I thought I heard somewhere have some Caribbean descent but cannot confirm)Ryan Bertrand - D - Chelsea/England (I'm not sure but I would guess Dominica)
Shaun Cummings - D - Reading/England (maybe Jamaica)
Antonio German - F - Stockport/England
Jason Jarrett - M - Oldham/England
Zat Knight - D - Bolton/England (has two caps for England but both in friendlies, he may be Lucian)
Izale McLeod - F - Barnet/England
Ishmael Miller - F - West Brom/England
Kyel Reid - M - Bradford/England
Brian Smikle - M - Cheltenham/England (I believe Jamaica)
Danzelle St Louis-Hamilton - G - Darlington/England
Jordan Stewart - M - Millwall/England
Ineligible:
Albert Jarrett - M - Barnet/England (played for Sierra Leone) (I think he might be of Jamaican parentage)
**Means they'll likely never play for them again
I'm sure I missed some obvious ones, but I'm tired so give me a break