Here’s a free tip for you.  If you’re traveling to the DC metro area and need to find a place to stay around $100/night but don’t want to stay in a flea-bag motel or 100 miles outside the city then you might consider the Comfort Inn right off the Beltway at the Van Dorn exit.  It is literally right off the exit so you can be on the Beltway in 30 seconds and from there you can be on 395 north to DC in five minutes or to the Wilson Bridge in five minutes (without traffic).  Even better they provide a free shuttle to the Van Dorn Metro Station, which is about a 1/2 mile down the road.  You can also take Eisenhower Avenue into Old Town Alexandria without having to get on the highway. 

As far as amenities go the hotel is nothing fancy, but it’s clean and the rooms don’t smell like an ashtray.  The staff was efficient when I stayed there, and the bed was comfortable.  One problem is that if you’re on the Beltway side you can hear the hum of traffic but it’s easily drowned out by the TV on low volume and really it’s white noise.  All in all it’s an economical place to stay without the inconvenience of being in the hinterlands.