I join the others who said "Bedknobs & Broomsticks"... easily one of my favorites as a kid. Since re-make fever has hit Hollywood in recent years, maybe it's only a matter of time before that one gets re-made.
Incidentally, a number of films mentioned here were considered for rides, and concept art for some (Black Cauldron, Love Bug, etc.) can be found here:
Lost Disneylandia | Progress City, U.S.A.