Zimride has already established large ecosystems of trusted corporations and colleges with riders that plan and reserve trips well in advance. It has now raised $1.2M to develop a smartphone application in iPhone, Android, and HTML 5 to facilitate last minute trips with minimum effort.
Background
Carticipate bills itself as 1st mobile ride-sharing app w/ location-based platform
Weeels is another ride- and taxi-sharing service w/ mobile at core
Avego also has already launched its iPhone app to dynamically find open seats in carpools