I sold my pickup truck after I moved to Seattle in 2000... I have a little scooter I use to get to work and back (10 min ride), which costs me maybe 3$ in gas a week... but other than that I don't have a vehicle. Bus gets me most places for free, if I really need a car for something I either get a FlexCar (car-sharing program we have here) for a few hours or just hit up Enterprise and rent one for the weekend.
Pro tip: reserve a car with Enterprise (probably other places too) and they have to honor the rental price you sign up for. So I always get the cheapest weekend deal available, which would generally put you in something like a Geo Metro... But figure out when their lot is low on vehicles, like, late on Friday afternoon. Then when you go to pick it up and all they have is premium vehicles, you get whatever they have available for the same price! They'll try to upsell you but just say no thanks... they have to give you a vehicle and you still pay the same price. I've driven Jaguars, Escalades, Chrysler 300's... for the 20$ a day tin-can-on-wheels rate.

Costs FAR less than paying for parking, insurance, maintenance, license tabs, etc... literally saves me thousands per year.