According to the Hummer website, it is a specially commissioned track by a music house called Robot Repair.

You could try contacting the company directly...
Their site has a bunch of songs on it that you can listen 2. But there are so many it could take a while to actually find the one in the Hummer commercial. But it does seem that they have most of the music. If you have time to search or are bored. Please help, Thanks so much! -Jared
ok, here's the problem. all the "tracks" on that site are only 30 seconds long about. they are only samples. so even if you found the right track by sorting through all of them you'd only have 30 seconds of the song... if you think that's worthwhile then go ahead and search, and maybe i'll put in a little time. but honestly, if it was me, i wouldn't find it to be worth the time.
What's the song in the Hummer car commercial with the three bears?
According to the Hummer Website, it's an original composition by a music house called Robot Repair.

If you go to, scroll over "Hummer World," and then click on "TV Commercials," you can watch their ads. They all usually have music information with them too!