Zipcar's 9,000-plus fleet of vehicles has brought the car-share model of urban transport to 15 metropolitan areas in the US, Canada, and the UK. A $60 annual fee gets you in, and rates start at $7.75 an hour (gas included). Tell the app where and when you need a ride, and use the virtual key fob to unlock the car when you arrive.
WIRED Search by vehicle type. Cheaper than car insurance.
TIRED Limited geographic availability. App is slow to load.