Indian in DC itself ranges from very good (and expensive) to average (and over-priced). I can't speak to places in the suburbs, as I don't frequent them.
Probably the best place in DC itself is Rasika. It has two locations: 633 D St NW and the West End one at 1190 New Hampshire Ave NW.
If either of those are too rich for your budget, then I'd suggest Indique, which is right at the Cleveland Park metro stop on the Red Line.
If you like your curries served in a somewhat old school Raj-esque atmosphere, I'd suggest The Bombay Club, down by the White House.