Bicycles are way cheaper than I remember them being. I jsut got one at Wal-Mart tonight for $90, and it's pretty damn sweet from what I can tell.
The main reason I need a bike: I have no car. I can get most of the important places in town on foot, (indeed, I can get anywhere as I found last night =) but a bike will make the other side of town much more accessible. Not to mention it's been forever since I've ridden my old bike, and I wanted to get back in the habit.