Most days I ride to campus from Westwood.
It's easy to get the impression that in order to bike to work you need to be a twentysomething hipster or a zero-body-fat racer. I'm clearly neither! I started slowly and worked up to the full commute over a few months.
There are lots of altruistic reasons to commute by bike, but I just think it's a good use of time. When I drive to work, I feel like the time is lost. Public transit is a bit better because you can work, but at least for my commute it's not very efficient (drive to commuter rail, ride to south station, transfer to red line, walk to building).
Here are a few links with great information about bike commuting:
Here's my commuter, a Xootr Swift folding bike. I bought the frame and built it up with drop bars, BMX stunt wheels (for the Boston potholes), and an 18-speed drivetrain (stock is 8). Fenders for the rain and a rear bag for carrying stuff. And if it really starts pouring, I can fold it up for the subway and commuter rail. Otherwise it's nearly as fast as my road bike. Full story here.