We loved the Hyatt Arlington. See http://gettingoutofdcweekendgetaways.blogspot.com/2013/07/romantic-stay-in-arlington.html.

Also try hotwire and priceline. The marriott wardman park has come up under $100 and so have other 3* or higher places.

Not sure what part of DC you're looking for, but our in-laws have had very good luck with the two Residence Inns in Old Town Alexandria (close to both Eisenhower and King St. Metros). While these can be hella expensive during the week, my mom has found some great sub-$100 weekend deals in the past, and often ends up with a suite w/separate bedroom. Marriott offers both AAA and senior discounts.

Lately I've had good lukc with kayak.com, hotels.com, and booking.com

Got it...thanks all!

Your best bet is to go to one of the hotel aggregator sites (hotels.com, kayak, etc) and see who has a deal at the moment.

Howard Johnson on NY Ave is $85/night on hotels.com

or the Holiday Inn Express at NY Ave and Bladensburg Ave NE (which has a shuttle to the metro) is $126.

I know people who like the Dunn Loring Courtyard Marriott for cheap and close to the metro. You might also find something in Crystal City or Bethesda depending on the dates.

In-laws are coming to visit in October. They need a hotel for the weekend; I'd like to find something near a metro that they can afford. Think less than $100 a night...they're coming from upstate NY so the sticker shock of DC will be an issue. They don't need anything fancy; just clean and cheap. Tia.