flinc.org is aiming at both the city-to-city ridesharing market (like Zimride or GoLoco) and at the “spontaneous” market (e.g., one-time trips).  See flinc's features page.

flinc believes they are the only service to combine these three elements: GPS navigation devices; smartphones; and social networks.

flinc CEO Klaus Dibbern says, “flinc is fully integrated with NAVIGON's iOS solutions. The driver can accept passengers even while driving, he is being directed turn-by-turn to the pick-up point (which can be any address) and to the drop-off location (which can also be any address). flinc's intelligent route matching algorithm calculates the detour.”

There is a press release, an article based on flinc's demo in 2010, and a wikipedia entry (in German).

Slides from a presentation at EcoSummit 2011 (March, in Germany) are available here.