Suggestions for Washington, DC at end of March?

I'll be in Washington, DC at the end of the month.  I like Washington.  It's fun, historic, and exciting.  I have always enjoyed my trips there.  Unfortunately, my visits are usually very short, and fairly busy, with lots of meetings, and little time to explore.  I don't really feel like I know the city well.  I'd be grateful for suggestions for neighborhoods or locations that are interesting to photograph at night, and I suppose are safe.  Right now I don't have too much in the way of photographs for DC.  Indeed, I think all I have posted are pictures from the Metro, from a trip last year:http://blog.canghuixu.com/2010/03/washington-metro-march-2010.html

Also, it looks like I may be free on the evening of 4/1, or at least part of that evening, so I would be grateful for suggestions for things to do then...  performances, gallery openings, happenings, shindigs, hoe-downs, soirees, whatever...