Yesterday, Paris began its Velib' program (velo + liberté = velib'). A program where eventually over 10,000 bicycles will be available to Parisians for their daily commute at 750 different points throughout the city. All it takes is a 150€ deposit, and, while the first half-hour is free, one also needs to sign some sort of rental agreement, depending on needs. The best deal seems to be the annual 29€ rental.
I don't know if that would work in SF, because of these.
Article from La Liberation