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 Opportunity
Innoventions Photo Line (Mickey,Minnie, Goofy, etc)
Chip n Dale at the Land Dining
Donald in Mexico
Mulan and Mushu in China
All the Princesses in Norway Dining
Snow White in Germany
Mickey in American Adventure
Pinoccio in Italy
Alice and Mary Poppins in the UK
Marie, Remy, Belle, and the Beast in France
Aladdin, 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.
One of my most favorite perks with the Disney Visa is the private audience that you get with Mickey and the Gang at Innoventsions at EPCOT. Depending on the line outside, you can get a "photo shoot" that will include a Disney photographer and your camera for between 3 to 10 minutes. Thats right! You get a bit of private time with Mickey, Minnie, Pluto, Goofy, and Donald! AND YOU GET A FREE PICTURE OUT OF IT!!!
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!