Zimride is a handy service that facilitates finding rides, whether it be a commute, one-time ride to an event, or a carpool back home for Thanksgiving break.
The website is pretty user-friendly, and it integrates with Facebook (for your Facebook-stalking convenience... just kidding). If you need a ride, you can post when and where you are looking for transportation, and you can browse for rides being offered. If you have a car, you can post a ride, say if you're going home one weekend or for a break. Zimride helps find potential matches for you, and can send you email alerts you when they are found.
For trips to or from out of town, ridesharing is a good alternative for people who can't afford the cost or time to take the bus or have a lot of cargo. It's much cheaper (for everyone involved) to share with multiple people, or even just one person, than to drive yourself. It also means less cars will be on the road, reducing pollution and fossil fuel demand.
I used Zimride earlier this summer to get home, and it worked out great for me. While most of the longer-distance rides are to the major cities in the Northeast, the more people that start using Zimride, the more community resources (i.e. rides) will be available, and the more effectively we can meet each others' needs and reduce our collective carbon footprint.
Check out Way2Go for more transportation options.