I would have used it. I used to ride with a van pool. Links:

http://www.vanpool.com/ (sponsored by Enterprise rent-a-car)

http://www.vanpoolusa.com/ (sponsored by VPSI Inc.)

This was in Southern California, where public transportation has been endangered or extinct for decades. The arrangement sucked, and my current commute sucks enough that I'd carpool again if the meetup time wasn't 5:45 a.m.

Edit: I poked at it a little, and noticed that it doesn't ask for a radius when saving a new commute (no matches). Is the matching algorithm fuzzy enough to figure out when I'm "close enough" to someone else's route? Does it match along the whole route, so I could pick someone up midway?