Ok, 7 yr and 20 month old children here. I'll reply to the first reference to 'Sesame'.
6 years ago I found a 'Sesame Street Baby' CD at a local discount store. My then young son loved it.
I loaned it out a few years ago and it was subsequently lost.
A few months ago I bought 'Sesame Street First Steps', which is basically the same game. You can find it for sale on other websites, and I would discount the negative reviews. They don't quite get it. It has keyboard and mouse games. I have a ~9 year old USB 1.1 track ball that I used for both my children initially, but they quickly picked up the accuracy of my laser mouse.
For fun and introducing them to computer controls, I haven't found anything better.
Of course, videos games for toddlers are not a baby sitter and I Always play this game with my child on my lap.