SpaceShare Green Travel -- carpool, community building
SpaceShare Green Travel builds ride- and room-share tools for festivals and conferences. Our sister effort Verdant Event builds complete websites for conferences with greening tools integrated.
The best solution for carpooling to work is typically the one provided by a government-subsidized program for your city. In the San Francisco area, that's 511.org. Just google commuter carpool program (your city.)
For Washington DC and into San Francisco, you might explore casual carpooling: informal pick-up points where both riders and drivers line up.