Well, this is one of the most popular topics here on the DIS, and we love to talk about it!
As fas as restaurants that require a PS (as opposed to counter service), I like:
Carnation Cafe (in DL - the seating is limited and the line builds quickly, so definitely make a PS if you can; this is the only place in DL that sells the full-size Mickey Mouse waffle, I think)
Wine Country Trattoria (in DCA)
Goofy's Kitchen (character meal in the DLH)
Storytellers Cafe (in the GCH - not necessarily the character meal, however)
Rain Forest Cafe (in DTD)
Naples (in DTD)
ESPN Zone (in DTD)
As far as counter service meals:
Bengal BBQ (DL)
River Belle Terrace (Home of the Mickey Mouse pancake in DL)
Blue Ribbon Bakery (try the excellent cinnamon roll)
Taste Pilots Grill (DCA)