"Community gardening is one of the hottest pastimes sweeping the country!", proclaims an email announcing that construction of the community garden at Bruce Monroe Park (Georgia Avenue between Columbia and Irving Streets) will commence tomorrow at 9am. Aside: I'm not sure if tomorrow is the best date to begin this endeavor, as crowds from the Caribbean Parade will be rather...massive, which might inhibit construction just a bit. In any case, if you're interested in helping with the buildout or in reserving a garden plot, go here.
Additionally, check out the DC Foodshed Map, created by Ecolocity DC. Looks to me like a pretty comprehensive listing of community gardens (the Peabody, Madison Street, and Fort Stevens gardens in Brightwood are represented, as well as the Takoma Rec Center and Blair Road gardens) as well as co-ops, urban farms, etc. Contact info is listed for most, so if you're looking for a community garden plot near home, here's your resource.
View Washington DC Area Foodshed in a larger map
UPDATE! Bruce Monroe Garden organizer has informed me that they hauled their stuff yesterday, so the parade should not impede their progress. All is right with the world.