Via a NYTimes article, a cool new service called Avego Shared Transport (tm) that uses an iPhone client, a web client, GPS, GIS, SMS and micropayments to connect people who need a ride with people who have extra space in their cars.
When I commuted in Seattle I did it alone, along with many other drivers. While rideshares are a great idea, sometimes they are not practical, especially if you plan on running errands during your commute. A system like Avego, the Times notes, is that Avego's approach does not require the commitment to a ride share or carpool. Instead, commuters can make available seat space to riders as the driver sees fit.
The iPhone app is in beta. It will be interesting to see if the iPhone-toting commuters pick up on the app and build the critical mass to make this a powerful social networking app that helps cut down the number of cars on the road.