So to answer your question, EPCOT! Even if you do not have a Disney Visa, EPCOT has a very nice and convient set up where you can go character to character to character with nice backdrops near Innoventions!
It is a bit of a shock now thinking of it that EPCOT is probably the best place to meet characters. They have:
Disney Visa Photo OpportunityInnoventions Photo Line (Mickey,Minnie, Goofy, etc)Chip n Dale at the Land DiningDonald in MexicoMulan and Mushu in ChinaAll the Princesses in Norway DiningSnow White in GermanyMickey in American AdventurePinoccio in ItalyAlice and Mary Poppins in the UKMarie, Remy, Belle, and the Beast in FranceAladdin, Jasmine, and the Genie in Morocco
Not to mention holidays around the world!
Wow, never thought of it!
The only other Character meet and greets I would recommend would be to try to attend a special event such as Mickey's Not So Scary Halloween Party. There are so many characters out that you normally do not find, with many opportunities to get a photo and such. I know that during this is usually the rare time that you can get all seven dwarfs and Snow White in one picture, villains, and characters dressed for the holidays.