Thanks to Jill Boone, the Climate Change & Sustainability Manager for Santa Clara County for sharing this link. It's a tool from Kiplinger that lets you calculate your cost savings when you ride your bike to work instead of driving. If the rate seems a little high, keep in mind that maintenance and repairs are factored in, too, not just gas. Of course, if my car breaks down again the best way to fix it will just be a little gas... and a match.
Calculate your savings at http://www.kiplinger.com/tools/bike/index.php.