I hate to admit that it took reading a book to think to tape a picture in the bottom of a box, but I actually got the idea from Gymboree's Toddler Play.
When I discovered this activity to help fine motor development in toddlers, I was sold. All it took were some dollar store pom poms and an old egg carton. Once Liam discovered how much fun it is to scatter the pom poms all over the floor, he was sold, too.
Check out other cheap (or free) activities here.