Try
www.dogfriendly.com/
which gives (for DC)
Crowne Plaza -14th and K Street NW Washington
Hotel Helix -1430 Rhode Island Ave Washington
Hotel Madera -1310 New Hampshire Ave Washington
Hotel Monaco -700 F Street NW Washington
Hotel Rouge -1315 16th Street NW Washington
Hotel Sofitel -1914 Connecticut Ave Washington
Hotel Washington -515 15th St NW Washington
Marriott Wardman Park Hotel -2660 Woodley Road NW Washington
Motel 6 - Washington -6711 Georgia Avenue Washington
Park Hyatt Washington -1201 24th St NW Washington
Red Roof Inn - Washington, DC - Downtown -500 H Street Northwest Washington
Residence Inn by Marriott -333 E Street SW Washington
Residence Inn by Marriott -2120 P Street NW Washington
Residence Inn by Marriott -1199 Vermont Avenue NW Washington
The Fairmont, Washington DC -2401 M Street NW Washington
The Jefferson Hotel -1200 16th St. NW Washington
The Madison, A Loews Hotel -1177 Fifteenth St. NW Washington
The Quincy -1823 L Street NW Washington
The Westin Embassy Row -2100 Massachusetts Ave. N.W. Washington
The Westin Grand Washington DC -2350 M St. N.W. Washington
The Williard - Washington -1401 Pennsylvania Avenue NW Washington
and
http://www.tripswithpets.com/state.asp?dest=DC
Hotel Helix, Washington
Hotel Rouge, Washington
Motel 6 - Washington, Washington
Red Roof Inn - Washington, DC - Downtown, Washington
Alexandria/Arlington/Crystal City (Just south of DC - close to that 5 sided building)
http://www.dogfriendly.com/server/t.../cities/usonlinecityVANorthern_Virginia.shtml
Holiday Inn Hotel and Suites -625 First Street Alexandria
Quality Inn Mount Vernon -7212 Richmond H Alexandria
Red Roof Inn - Washington, DC - Alexandria -5975 Richmond Highway Alexandria
Residence Inn by Marriott -1456 Duke Street Alexandria
Sheraton Suites Old Town Alexandria -801 North Saint Asaph St. Alexandria
Residence Inn by Marriott -550 Army Navy Drive Arlington
Residence Inn by Marriott -1651 N Oak Street Arlington
Sheraton Crystal City Hotel -1800 Jefferson Davis Highway Arlington
Sheraton National Hotel -900 South Orme St. Arlington
The Westin Arlington Gateway -801 North Glebe Road Arlington