I'll do the English cast but I can look up the Japanese too. I'll also do the canon characters if I can.
Past and currently:
Ash/Delia/May - Veronica Taylor
Brock/James (episode 10-current) - Eric Stuart
Misty/Jessie - Rachel Lillis
Meowth - Maddie Blaustein
Max - Amy Birnbaum
Professor Oak - Stan Hart
Tracey - Ted Lewis
Jenny/Cassidy - Megan Hollingshead
Gary/Butch - Matthew Milter
Harley - Andrew Rannells (I don't know Drew's at the moment)
Joy - Hollingshead but I'm not sure with her that or Ortiz.
Narrator - Currently Mike Pollack, I'm still tracking down the original.
Kanto GLs:
Lt. Surge - Blaustein
Erika - Leah Applebaum
Sabrina - Lisa Ortiz
Koga - Ken Gates
Blaine/Giovanni - Ted Lewis
Elite Four:
Bruno - Blaustein
Lance - Wayne Grayson
Johto GLs:
Falkner - Nathan Price
Bugsy - Tara Sands
Whitney - Hollingshead
Morty - Rannells
Jasmine - Not sure.
Chuck - Dan Green
Pryce - Jimmy Zoppi
Claire - Hollingshead
Hoenn GLs:
Roxanne: Kayzie Rogers
Brawly: I think it's the same guy who does Sonic. Forget the name at the moment.
Wattson: Green
Flannery: Ortiz
Norman: Green
Winona: I'm not sure.
Tate and Liza: Not sure there.
Juan: Not sure.
Steven: I'm rather sure Pollack does his voice but he did a real good job masking it.
And for the villains (including the movie ones):
Mewtwo: Phillip Barlett in the movie, Green in the special.
Lawernce III: I believe it was Neil Stuart.
Entei (third movie) - Green.
Vicious/Iron Masked Maruader - Green
Annie - Hollingshead
Oakley - Ortiz
Bulter - Grayson
Diane - Hollingshead
And for the orgs.
Rocket:
Sebastian - Eric Stuart
Namba - Zoppi
Domino - Working on it.
Haven't seen the Raikou dub, so I don't know who did Atilla and Hun. Although I have heard people said Atilla is Marc Thompson.
Tyson/Dan'in - Green
Magma:
Maxie - Thompson
Harlan/Homura - John Campbell
Aqua:
Archie - Sean Schemmel
Isabel/Izumi - Rogers
That's it for the main cast and supporting cast. Anyone specific, you'll have to tell me and I'll dig it up.
