A bike may actually save you money. I don't know if you ride the rocket (a misnomer if ever there was one), but at $2+ a trip, a bike can save a lot of money over the course of time. If you're a metropasser, you may ride enough that you can ditch the pass and pay as you play. Same goes for gas at $0.85/litre.

Sit down and do some math, a good used bike may pay for itself in a hurry. Don't forget to check out the garage sale bikes. Oscar's 3 step method will work equally well with a garage sale bike. A friend of mine once said that the first bike you buy will show you what you want in a bike and the second bike you buy will be the one you like.