Here are some photos of forehand grips.
I am only looking at forehands here because they are harder to learn, less intuitive (ask any non-ultimate player to throw a disc, and they will generally throw a backhand, not a forehand), and there is more variation in them, among Ultimate players.
Most players should use a power grip. (Scroll down to 3.2). I am certain about this.
Jeff Cruikshank, Furious George, thrower extraordinaire. I recommend having your your ring finger and pinky fingers straight, and supporting the outside of the disc, like Jeff does.
Miranda has the pinky and ring fingers bent.
Tom Rogacki, Chilly, who has huge hands
Meg Campbell, Ishtar
Split finger/Beginner's grip
Still looking for good examples...