I did the Potomac/Anacostia circuit this morning and saw the following:

On Potomac between 14th St. & Memorial bridges
2 Long-tailed Ducks (seen at 7:30ish, but gone by 9:30)
4 Surf Scoters (incl. 1 ad. male, still there as of 11:45)
1 scaup, sp (I'm going back and forth on this, but currently think
Lesser)
13 Buffleheads
1 Pied-billed Grebe

Hains Pt.
3 scoter, sp. as they flew down the Anacostia and out of sight

Anacostia River Park
4 Hooded Mergansers
1 Surf Scoter
3 Bufflehead
1000 Laughing Gulls (again, a very rough estimate - they were streaming
up the river at a steady pace, all but 2 adults)

Lots of geese around(c.750), but all were Canadas, except for the
domestic/Graylag thing at Kenilworth Park.

On a personal note, this is the first time I've seen all 3 species of
scoter in DC in one year.  Break out the champagne!

Good birding,
Paul Pisano
Arlington, VA