Believe it or not, I've been riding my bike to work. The GPS says that it's about 9 miles one way, and after doing it now for three weeks - I'm averaging about 3 days a week (sometimes I just have to drive into work for various things).
Most of the way is on a bike path, and Patrick made me get a helmet (I have a tendency for head injuries). However, there are some times when I have slammed on the brakes to avoid a car making a turn in front of my lane.
When I first started I got a little lost, and I was out of shape (still am); but now instead of 45 minutes one way, I've got it down to 30 minutes. When you consider it takes that long to get to work (or longer with traffic), it's not a bad deal.