The Wall Street Journal notes the surge in interest for cask conditioned beers. Delivered in casks, they rely on natural pressure and a hand pulled lever to maintain flow. No nitrogen or CO2. The method is often used by brewers for experimenting, as the cask can be sampled, new ingredients added, and closed again. That's not the case with sealed, pressurized casks.
Bronx Brewery was singled for its Cask Parties at the brewery.
Church Key / Birch & Barley in the DC area
Lord Hobo in Cambridge MA
Max's Taphouse in Baltimore MD (looks like a few minutes off I-95)
Ashley's in Ann Arbor MI
Daily Pint in Santa Monica CA