We have a 6 month old and just returned from 3 days at Disney. We took her on It's a Small World and she looked around and liked the dolls and the singing. She also rode the Haunted Mansion, but she had a bottle so she wasn't up and looking around. We rode on the Railroad from Main St to Mickey's Toontown and then back to Frontierland. My wife uses one of those cloth sling things that keeps her attached without hurting her back like the baby bjorns so we did the Swiss Family Tree House and that was fine. Jungle Cruise was also easy.
I think Peter Pan, Winnie the Pooh, Snow White would all be fine. Also, any of the shows are fine.
Possibly Pirates of the Caribbean, but there is that initial drop that might be too much for a baby.