MY DD was tall enough for the following (DD is short for her age- in the 25th %tile):
Height requirement:
35"- Barnstormer- she was tall enough on her first visit at age 3 1/2, but she didn't ride- she is definitely NOT a thrill ride lover!
38"- Kali- see above
40"- Dinosaur, Soarin', Test Track, BTMRR, Splash, Stitch, Star Tours, ToT- age 4
44"- E:E, Mission:Space, Space Mtn- age 6
48"- Primeval Whirl, RnR, most slides at the waterparks- age 8
51"- CyberSpace Mtn and Buzz Lightyear (both at DQ)- age 9
52"- Tomorrowland Speedway (to drive alone)- not tall enough yet- probably age 10.