Uber, the free mobile smartphone app, that allows you to call a driver to pick you up at your location, and you to pay within the app, rate your driver (or if you’re a driver, rate your passenger). Initially, Uber started out focused on town cars, but it has since expanded into SUVs and taxis, though the exact selection varies by geography. The service is now available in DC, NYC, Chicago, Los Angeles, Miami, San Francisco, and Dallas.
The Uber iPhone/Android app pulls location data from your phone and Foursquare, and allows you to enter in your destination, and provides you an estimated fare before booking the service and charging your credit card. If you don't have a smartphone you can log in using m.uber.com. Its that simple, no cash, no hassle, no tip.