Bicycling is the best way to see a city.
If you agree with that statement, you'll want to sign up with liquid.com. It's a new worldwide network of bike owners and would-be bike renters that seeks to connect the two groups with an ease never before attained. Through Liquid, bike owners rent their bikes to travelers, cyclists, and even bike-less locals that are just looking to get in a bit of exercise or exploration time in over 400 cities in 80 countries.
The initiative launched in New York City and San Francisco last April, and in September it started a national beta program.