BabyBash - kids love it!
A few months ago, I saw Toby Reyelts' post about a game he wrote called BabyBash. I downloaded it when I first saw it and let Abbie play it. She loved it immediately, and would ask me to play it whenever she saw I was "working" on the computer. Of course, she'd say "Daddy - no working" first, and then say "play Abbie's game?".
Then I lost the link for a couple of months and this conversation turned very sour. A couple of weeks ago, I found the link and vowed to never let it go again. This morning, I gave Jack a run at the game (he's almost 8 months now) and he loved it too! It probably doesn't hurt that they're playing it on a 23" display. 
If you've have small children, you should really let them try this game. Thanks Toby - you rock!