My son is a little bit older (just turned 4) but I realized that he had TOO many toys out... he couldn't find anything to play with, and had 100s of toys laying around... So I boxed up everything that he hasn't been playing with and only left few favorite things. The rest can be rotated later. Between 3.5 and 4, my son loved, LOVED and still loves playdoh, got lots of little plastic tools to cut and mold. Also, he is very obsessed with fire trucks, police cars, taxis, always playing with little matchbox cars. He is not interested in his bigger cars or trucks anymore, only little ones. Whenever we go to the zoo, he gets all his little plastic animals out and plays with them, and from time to time dinasours. What about outside play like a bike or scooter? My son loves any kind of outside play, even if it's just playing with rocks, or sticks, just free play. And he did not go to school until he turned 4, he was at home full time with me, and now at 4, all he wants to do is write letters, and numbers and read:) Also, I think at that age, kids need some ideas sometimes, of what to do. If I see my son is bored I take out puzzles or blocks or paints and organize activities for him.