In addition to helping you find your partners-in-commute, the site also offers an array of tools that allow you to keep track of shared carpooling expenses and schedules as well as a way to notify the rest of your group in case you can't make it.
Based on the success of other social networking sites, carpoolcrew.com sounds like a great idea. I typed in a couple different zip codes on the East and West coasts but wasn't able to find any other commuters in those areas. It's understandable given that the site's only been around for a little over a week.
[Source: Carpoolcrew.com via Energy Bulletin]