Hey, I was just at a puppet festival in Grand Rapids this past weekend. I took a puppet voice workshop and the instructor, a ventriloquist, taught a real simple methodology of creating voices.
She gave a few different kinds of voices to experiment with. Since you can't hear me, I added little notes to explain what she meant (from my perspective)
Nasal (as if you have a cold)
Gutteral (think Wolfman Jack)
Falsetto
Dopey (Bullwinkle Moose)
Whisper (Kinda like Marilyn Monroe with lots of air)
Melodic (hard to explain, but if you speak with an Italian accent and your voice kind of fluctuates, that's sing-songy)
Anyway, the point was to mix and match one or two, then change your voice pitch, speed, intonations, volume, etc, to create a larger voice library.
While I certainly can't reiterate the whole session here, I wanted to share a bit. It really was a great festival and alot of fun.