Drijo is an interesting concept in ride-sharing on Google Maps that allows people to auction off available seats in their car or search for free seats in other people's cars.
If you are looking for a ride you enter your starting point, destination and the date you wish to travel. Drijo then searches for rides that have been offered on that route and lets you enter a bid for the journey as you would for an item on e-Bay.
Like e-Bay the auction has a time limit and it is possible to view the highest current bid.
Drijo also allows users to submit car-pooling routes or search them in order to find others to start carpooling for regular routes to regular destinations. The site is available in English, Spanish, French and German.
RoadSharing.com is another car-pooling service that provides an easy way to find someone to share a trip with. RoadSharing provides a meeting point between those offering lifts and those in search of a lift.
You can add a route or search for existing routes on a Google Map. Currently most of the available routes seen to be in Italy. However the site is available in English, Spanish, French and Italian so could easily become popular in the rest of the world.
Other Carpooling Google Maps
eMotorPool.com - Google Maps carpool search
Carpool - Google carpooling Mapplet