There is a new ridesharing app/website named PoolXing - www.poolxing.com where finding and connecting with carpoolers is easy and intuitive.
The more the people start using it, the more useful it will get.
More Info: PoolXing - Connecting Commuters. PoolXing (Poolers Crossing) is a ridesharing service to find and connect commuters having similar origin and destination points. It helps commuters to search for ride requests or to post their own request by entering start & end address and date & time. The service also provides an inbuilt messaging and notification system for riders to interact with each other.