I've had it on tap at RFD in Chinatown (http://www.lovethebeer.com/), although that was months ago and their tap list changes frequently. The Brickskeller (RFD's sister beer bar near Dupont) has several other Russian River beers in bottles, but not the Pliny the Elder. Other places that *might* have it include Rustico (http://www.rusticorestaurant.com/bar.htm) in Alexandria or Birreria Paradiso (http://www.eatyourpizza.com/about_birreria_paradiso.php) in Georgetown. If they don't, there are other great beers there (and good food), so it wouldn't be a total loss. :)
As for a store, the broadest selection in DC is at Chevy Chase Wine & Spirits (http://beeradvocate.com/beer/profile/1760). The Vienna Whole Foods (http://beeradvocate.com/beer/profile/4086) also has an excellent selection.
Excellent choice in a West Coast DIPA, by the way. Its one of my favorites. For those who aren't familiar with it: http://beeradvocate.com/beer/profile/...
best shot for beers out of the norm in Baltimore area is Well's Liquors on York Rd. Belair area, maybe WineWorld off of rt24 (Abingdon) or Jim's Bottles up RT1 near Hickory. I understand that Stone's Brewery is about to be distributed in the area, so can Russian River be far behind?