The Plaza on Main Street has ice cream and sundaes, and if you want to feel like your miles away from the crowds, take the raft over to Aunt Polly's on Tom Sawyer's Island and get an ice cream (they have apple pie, too, but check if it's open as it is seasonal).
A lot of places at WDW have Edy's ice cream, which is sold all around here at any supermarket. Just your average ice cream.
One place that I've never tried for ice cream but looks great is Gairadelli's (sp?) over in DTD. Their sundaes look tasty!