Citi Bike is New York City's bike share system. Columbia has no affiliation with Citi Bike, but it is a good choice for getting to your destination faster or for a recreational cruise.
Citi Bike offers short term memberships which are ideal for visitors, or annual memberships for frequent users. Depending where you live, you might benefit from combining Citi Bike with your subway commute. You'll get more exercise and may even achieve a more enjoyable commute.