MAG, be sure to pick up a copy of the Friday Washington Post (newspaper) -- that'll have the Weekender section with non-musical/folk events. The Thursday Post has a calendar of community-level events; diff editions published for diff geographical sectors, and some nice lower-key events. Keep an eye out too for the (free) City Paper, which also lists interesting events.
If you were free earlier in the day, I'd highly recommend the Millenium Stage concerts at the Kennedy Center -- every day 6-7 PM, no admission, just parking charges ($8/car). A wide variety of performers; this past week Pierre Bensusan played a lovely guitar set. There's a website for Millenium Stage under the Kennedy Center's main page.