1) One of our biggest hits was a bounce house!  We use it indoors in the basement with a mattress at the end of it, and it's a big hit. 

I have them each see if they can bounce for 30 seconds.  They bounce and they try to hit balloons out while we put them in.

2) It's a little young for our kids, 5 and 7, but they liked the indoor golf.

3) Indoor basketball hoop over a door is lots of fun!

4) We painted rocks to leave in Unke's garden

5) Puzzles - lots of puzzles

6) And of course, board games and card games like "A Day at the Beach

7) Speaking of balloons, learning how to make balloon animals is fun!

8) Some recent fun books are: