One question I DO have for fellow DC mustaches, outside of the museums, what Mustachian things are there to do in winter in the DC area? We are still fairly new to the area, and work so dang much, that we haven't had a lot of time to explore.
It can be quite mild in winter in DC so that leaves open the possibility of outdoor activities:
Hike at Great Falls
Hike/bike C&O canal near Georgetown
Have a drink or tea at the Tabard Inn in Dupont while enjoying their lounge and fireplace. (To keep it cheap, just have tea and don't go into the restaurant to have dinner.)
Frederick Douglass house
Aquatic Gardens (requires car)
Kreeger Museum (costs $$ but is so worth it)
National Xmas Tree
Washington Monument (free)
Lincoln Memorial at night (romantic!)
National Arboretum near NY Avenue (best to reach by car)
Mount Vernon (costs $$ to enter but they sometimes offer a free day in January)
Nature Centers--many around in the suburbs