Better carpool networking

I have heard about systems of carpooling in San Francisco and the East Bay where people will meet and share transport, particularly between the City and East Bay. This is obviously a case of everybody wins. Carpools get fast track, share gas money, cut congestion etc. However, is there a place where people can get information on these carpools, where/when they leave? Could there be an online forum where people could make arrangements, perhaps ever for longer trips?