A group of volunteers in Portland, Oregon, have recently formed a Peak Oil Task Force to investigate the effects of rising energy costs in the city, anticipate future obstacles, and consider solutions that may help as price spikes continue. For their first trick, they've created Carpoolcrew.com, which is essentially an online matching service that gives people who want to carpool an easy means of locating convenient, well-suited ride partners.
This is much more refined than "Casual Carpool," the system I used to occasionally use in Oakland which simply designated a pick-up point where drivers and riders could converge. Now you can go online and type in a number of different criteria, somewhat like a dating service, to find other riders who live close by, enjoy the same music, have the same smoking habits, work the same hours, and so on.
The creators emphasize that this is for people who are "ready" to carpool; in other words, most people are still addicted to the sense of pure independence that comes from driving alone. But they forecast a change of mind about carpooling as congestion and oil shortages continue. "It's a solution waiting for a problem."