We went to MK early one morning just after rope drop. There were charecters everywhere! I have not seen that many different charecters in one location at any one time. We saw Cruella Deville, Mary Poppins, Mickey, Goofy, the Country Bears, and many many others. This was a great time to see many charecters. You evidently have to go early. At certain times in Epcot they pull a double decker bus around with loads of charecters too.
If you mean the citizens of Main Street, then there's pictures and names of some of them on this site: http://www.charactercentral.net/ViewCategory.aspx?CategoryId=13
They are a lot of fun!