M.S.
I love Hullabaloo! They are a San Diego kids band. We have 3 cd's and listen to them often. They are so good and fun to sing to that I often will play them even when the kids aren't in the car! LOL!! http://www.hullabalooband.com/
Other than that we listen to air 1 (here in the inland empire you can find it on 90.1) although it is a christian station, it's got music for everyone - it's postive music not so much worship. In fact they even play mainstream bands like The Fray, the good thing though is you never have to worry about bad language. My kids love and sing along to the songs. If you aren't in So. Cal, then visit their website to see if you have a station in you area. www.Air1.com
I just saw another Mom recommend Dan Zanes. We LOVE Dan Zanes over here too!!
Enjoy!
M.