I have a fond place in my heart for the SONYA (South of the Navy Yard Artists) Stroll, since I did my first stroll shortly after moving to the neighborhood in 2004. Plus, it's such a cool way to get inside some of the neighborhood's most interesting artist spaces. And a chance to support local artists. There's usually art for all price points - $10 earrings and $1500 paintings alike. The stroll takes place on Sat and Sun, 12-6, rain or shine.
Check SONYA's website for a map of artist locations. (My personal favorite stop is the Candy Factory building, 124 Washington Ave).