Nice hotel a few blocks from the National Mall (where all the museums are), overnight parking is $34 (and is valet). I checked availability, they had a Queen room available over the weekend at a rate of $150/night. Comes with high speed internet and a wine reception in the evenings (no breakfast though).
Hotel Monaco is in Penn Quarter, tons of great restaurants around and about 2 blocks from one of the best beer bars we've got in DC, RFD. Also within easy walking distance of 2 breweries, Capitol City Brewing and the District ChopHouse and Brewery.
So there's my contribution. There may be hotels with less expensive parking in the area, but I thought the room rate was pretty good given the location.