Lyft is a mobile-phone dispatched transportation company based in SF. You've probably seen the pink mustache cars - these are Lyft cars. The way it works is that when you sign up to be a driver, you drive your own car and put the mustache on your car when you're on the clock. Then people with the Lyft app can summon you to pick them up.

Their HQ is at 548 Market St. in the Financial District.