Fugazi. Fugazi. Fugazi. And they have a wonderful progression through their first album (released as "13 Songs" on CD), through their last ("The Argument").
And you can also go back to Minor Threat, if you are particularly enjoying the early stuff.
There is also an awesome archive of live Fugazi shows that is now available on the Dischord Records page.
They are the kings of the DC punk scene and an all around superb band. Bad Brains are another great option from around DC.
Up in Boston, there is Mission of Burma, who have also been putting out some solid releases recently in addition to their great classic stuff.
On the Chicago side of things, check out Naked Raygun, Big Black and Shellac.
West Coast stuff is better known. But for the West Coast, I'd start with Black Flag and Dead Kennedys.