When my DD was 2, we pretty much took her on everything except the rollercoasters. She was about 6 months old when we took her on Pirates at DL and she has been hooked ever since!
My DD just turned 2 and he pretty much goes on everything too -- when he's in a good mood.
Here's the only problem:
Both of my kids had a hard time with getting off the rides. They didn't understand that you had to leave. They wanted to stay on and go again. It's a challenge prying their hands off the vehicles!!
Some great rides for little ones:
At MK:
Pooh
Small World
The Hall of Presidents (it is air conditioned and dark --- nap time!!)
Tom Sawyer's island (they like to jump around, climb steps, etc.)
The Jungle Cruise
Transit Authority (It was called the People Mover at DL -- tomorrow land)
The cars
Dumbo
At AK:
The boneyard
The flying dinosaurs (forgot the name)
The Lion King show
Kilamanjaro Safari ride (my DS fell asleep our last trip

)
The train ride to Rafiki's conservation place
Epcot:
Energy (dinosaurs)
Crush talk (living seas)
The boat ride at the Land
Imagination pavillion (the ride plus the great hands on area)
Maelstrom at Norway
Beirgarten (fun place to eat)
Studios:
Bear in the Big Blue House
Hope this was helpful!