Originally Posted by RightD
IAD is approximately 40-45 minutes from DCA by car. If memory serves Washington Flyer (local taxi company) runs a shuttle between the 2 that is much cheaper than a cab would be.
Good luck,
- RightD
RightD is right. You can get the Washington Flyer. Or you can take the SuperShuttle. If cost is a factor, you can take the Flyer to the West Falls Church metro stop from IAD for $8 and then catch the blue line train directly to DCA. For more information, check out:
the FAQs at the Washington Flyer website
Also, DCA is in Arlington, VA and you have other options than at the airport itself. I live on the other side of the Maryland-Virginia divide, so I don't know where to recommend, but Arlington has hotels in every price range for every taste. You might do better to stay there than at the airport itself, but then you might have reasons to stay at the airport (early flight?).