Here's a fun one.
The folks over at Television Tunes (available here) have free downloads for thousands of the theme songs from television shows and movies.
The list includes everything from tunes that were popular of their own right -- songs like the theme from Hill Street Blues and others -- to fun jingles and well known songs from kids programs.
For example, go to their search function and type in "Sesame Street" and you'll find more than 70 educational songs from the popular series. Make a playlist and you've got hours of fun music for the little ones. Got older kids? How about Hannah Montana and iCarly.
I personally am going to start with the tunes from Glee.