If you are concerned about being stuck without a car, use car sharing through companies such as Flexcar, which has cars in Berkeley, Oakland and San Francisco. Plans start at $7/hr.

The non-profit City CarShare has cars throughout the area starting at $4/hr. And Zipcar has several hundred cars in the Bay Area starting around $7.50/hr.

A newer company called GoLoco, started by the founder of Zipcar combines ride-sharing, social networking and online payment.