You know, you're kinda late, aren't ya? I'm guessing you've never looked at the back of the KH manual. But yes, all these wonderful people have lent their voices. Here is the full list... There, that should stop other people from spamming like this.
order)
Haley Joel Osment .... Sora (voice)
David Gallagher .... Riku (voice)
Hayden Panettiere .... Kairi (voice)
Billy Zane .... Ansem (voice)
David Boreanaz .... Squall Leonhart (Leon) (voice)
Mandy Moore .... Aerith Gainsborough (voice)
Steve Burton .... Cloud Strife (voice)
Christy Carlson Romano .... Yuffie Kisaragi (voice)
Shaun Fleming .... Tidus (voice)
Dee Bradley Baker .... Wakka (voice)
Molly Keck .... Selphie Tilmitt (voice)
James Lance Bass .... Sephiroth (voice) (as Lance Bass)
Wayne Allwine .... King Mickey Mouse (voice)
Seth Adkins .... Pinocchio (voice)
Tony Anselmo .... Donald Duck (voice)
Sean Astin .... Hercules (voice)
Kathryn Beaumont .... Alice/Wendy (voice)
Jeff Bennett .... The Mayor of Halloween Town/Barrel (voice)
Jodi Benson .... Ariel (voice)
Robby Benson .... Beast (voice)
Susan Blakeslee .... Maleficent (voice) (as Susanne Blakeslee)
Brian Blessed .... Clayton (voice)
Corey Burton .... Captain Hook/Mr. Smee/The White Rabbit/The Doorknob/Floatsam/Jetsam (voice)
Eddie Carroll .... Jiminy Cricket (voice)
Pat Carroll .... Ursula (voice)
Dan Castellaneta .... Genie (voice)
Robert Costanzo .... Philoctetes (Phil) (voice) (as Bobby Costanzo)
Jim Cummings .... Winnie The Pooh/Tigger (voice)
Bill Farmer .... Goofy Goof (voice)
John Fiedler .... Piglet (voice)
Jonathan Freeman .... Jafar (voice)
Tony Goldwyn .... Tarzan (voice)
Gilbert Gottfried .... Iago (voice)
Jess Harnell .... Dr. Finkelstein/Lock (voice)
Naia A. Kelly .... Jane Porter (voice) (as Naia Kelly)
Linda Larkin .... Princess Jasmine (voice)
Eli Russell Linnetz .... Flounder (voice) (as Eli Linnetz)
Tress MacNeille .... Daisy Duck/Queen of Hearts (voice)
Kenneth Mars .... King Triton (voice) (as Ken Mars)
Mark Moseley .... Mushu (voice) (as Mark Mosely)
Ken Page .... Oogie Boogie (voice)
Tony Pope .... Geppetto (voice)
Kevin Michael Richardson .... Sebastian (voice)
Chris Sarandon .... Jack Skellington (voice)
Kath Soucie .... Sora's Mother/Shock (voice)
Christopher Steele .... Peter Pan (as Chris Steele)
Russi Taylor .... Queen Minnie Mouse (voice)
Audrey Wasilewski .... Terk (voice)
Scott Weinger .... Aladdin (voice)
James Woods .... Hades (voice)