Ok, I might be a little biased because I grew up in the area, but DC is an amazing city! I truly love it, and this will always be home for me.
Nearly all of the colleges and universities in DC have ridiculous tuition, because they're all private with the exception of the University of the District of Columbia. The major private schools are (and you may already know this...I'm just going to spew information):
American University
Catholic University of America
Georgetown University
George Washington University
Howard University
There might be one or two smaller private schools that I'm not aware of. Out of the schools listed above, I have friends who went to Catholic and GW for undergrad. They all loved their respective schools.
Are you set on going to college in DC? If not, Maryland has some great schools too. Here's a link to Maryland's public universities:
http://www.usmd.edu/ I went to a public university in MD, and absolutely loved it. If you're going to be living in DC, and possibly commuting to school in Maryland, the one that would make the most sense is the University of Maryland, College Park since it's closest to the District and has a Metro stop. College Park seems to be one of those love it or hate it types of schools. It is HUGE, so if you're used to a smaller school environment, it might not be for you (I personally would have floundered there). Even if you were to be charged out of state tuition, a Maryland school would be much more reasonable financially than a private school.
I don't know as much about the schools in Northern Virginia. I do know that George Mason University is there, but I don't know a lot about it in terms of academics or social environment.
I hope this helps! Feel free to PM me if you need more detailed information.