Islands of Adventure:
Spiderman and the Marvel Superheroes
Toon Character Zone (does not mention which characters)
Seuss Character Zone (does not mention which characters)
Universal Studios:
Spongebob Squarepants
Shrek and Donkey
Hollywood Character Zone (does not mention which characters)
Star Toons Shows
Madagascar Characters
Dora is usually found outside the Universal Studios Store, the one on the left right before you get to the Jimmy Neutron ride. Ask inside the store they can probably tell you the best times to meet her.
Most of them, the simpsons signs. The suess characters sign. Dora, Jimmy Diego, Alex the Lion, Madagascar Pengins, and Shrek have stamps that you can get.
For the autographs I recommend you use either sharpees or a regular or large pen (can also be bought). I recommend AGAINST the small (two inch) pens, as it is hard for the characters to sign with small pens.
As many times as I've been to Universal/IOA, I never knew you could meet characters until I went last year ....with that being said, we met Spongebob, Betty Boop, and Woody Woodpecker...
Check out both of my TR's forsome character pics. The Simpsons are usually either close to T2:3D or by the Kwik-E-Mart. I did notice they had some character meets in the expanded area in front of the entrance to HRRR. In my 2nd TR, that's where the Curious George pic was taken.