We stayed at the Hyatt Regency Washington on Capitol Hill. I booked it through Hotwire.com and we paid $159 a night plus tax, plus parking...we parked around the corner at $18 a day as opposed to Hyatt's valet parking garage at $40 a day.
The location was great! Click for a map.
The hotel was 70's style-ish...we didn't have a good view...room was a little dusty and older. The kids thought the lobby was neat. Pool was packed in evenings, had it to ourselves in the mornings. We never ate any of the hotel restaurants. Staff, especially concierge were outstanding. They charge $30 extra for a fridge for the stay (we used a cooler), and internet is another $10 a day if you want that...I felt they could have included those. But, again, the location was great (staff too), price was right (through Hotwire) and that mattered most.
I just checked the map and the Holiday Inn seems to have a great location as well...more in the middle of the mall, I don't know anything about the hotel other than location.
You should contact your representative right away regarding tickets to the Capitol, White House, Library of Congress (we skipped), Bureau of Engraving and Printing, and others. **For some of these you have to get tickets through a congressional member and it can take up to 6 months. You have to fill our security forms for the White House visit. We visited DC in February 2010 – I contacted Rosa DeLauro’s office in October 2009.