Ellen

Harry Shearer (sp?) of Spinal Tap fame (and many others), currently doing voices for the Simpsons:
C. Montgomery Burns
Waylon Smithers
Ned Flanders
Principal Skinner
Otto
Reverend Lovejoy
Dr. Julius Hibbert
Kent Brockman
Jasper
Lenny
Edde
Rainier Wolfcastle/McBain
Scratchy
Kang
Herman
George Bush
Judge Snyder