The only taller requirements I can think of are at Disney Quest and to do inversions on Sum of All Thrills. The Buzz Astro Blaster bumper-car style ride and the virtual Space Mountain at Disney Quest are 51". Kids can ride Sum of All Thrills at 48", but cannot do inversions until they are 51".
I could swear we did inversions at Sum Of All Thrills and my then 7 year old was *just* 48 inches. In the parks there was nothing she couldn't ride, but if I remember right there were some things at the water parks with a higher height limit.
You must be 52" to DRIVE on the Tomorrowland speedway, but other than that, 48" for Primeval Whirl, Rock'n'Roller Coaster and some of the water parks/Disney Quest stuff