Car-pooling doesn't suit everyone, so here's some info on an informal alternative -- slugging.
It's well-established in American cities such as Washington DC, and has evolved as a way to get around traffic-lane regulations. Only HOV's (High Occupancy Vehicles) can travel in the fast last, so it's in the interests of drivers to have at least two passengers or "slugs."
http://news.bbc.co.uk/2/hi/americas/3134002.stm
http://ie.youtube.com/watch?v=FMdQSFz_8ZA
http://en.wikipedia.org/wiki/Slugging
http://www.slug-lines.com/