Commercials seem to employ an inordinate number of kickin' songs, but uncovering those tracks can sometimes be a futile exercise. That's why Songtitle.info: Music from TV Commercials is so valuable. Every time I hear a great song in the background of an ad, I fire up my browser and head over to this site to get the low-down -- and the site never fails me. I'm not sure how they do it -- chronicling the songs and organizing them in a reasonable fashion must take serious work -- but the folks behind this site provide an excellent service that is definitely worth of a bookmark.
Incidentally, my current favorite song from a commercial is Citizen Cope's "Son's Gonna Rise," which was featured in a Pontiac ad from Spring/Summer '05. How do I know all this? Because Songtitle.info tells me.