he always really likes it when i fold him paper cranes. usually after i fold up the first one, there's a small strip of paper leftover from the original rectangle of paper that gets torn off, so i use it to make a few more little ones. What he likes to do is play "Mommy bird and baby bird." He'll ask the little ones if they want a ride, and then he stacks up the small birds on the wings of the larger bird and flies them around.
It's pretty cute stuff.
Also, yesterday he had a late nap and I had to wake him up (which was uh, awesome, by the way):