society for the preservation and promotion of the blues
in and around Washington, D.C.
They host education
al programs, monthly blues jams, and an annual blues festival
On a more mundane note, they maintain a calendar of local blues concerts, clubs, and events, because, when it gets right down to it, the only way to preserve the blues is to support the blues.
Individual membership's cheap, $15 per year. The organization is entirely volunteer run, so all their funds go towards events and such.
I've only been to one of their events so far, a blues jam at HR-57, and I was greatly impressed.