I fly out of DCA constantly and always, ALWAYS use Red Top Cab (202.328.3333). First of all, they're reliable and arrive at my office (West End) a couple minutes early every time. Also, as soon as we land in DCA I call them and by the time I get outside they're waiting. I charge each ride to my Corporate Diners Club card and the expense shows up usually within 24 hours.

I'd recommend using the everytime you fly!