Good Lord - what is there not to do around here? Tips? Try freaking everything - all of the different cuisines, museums, art festivals, concerts, etc. Visit the older areas, like Old Town Alexandria, where there is tons to do. Check out the off-beat (and often free) museums and sites.
If you take the Chinatown buses to Philly or NYC, stick with the name brands like BoltBus - the others are fly-by-nights with unqualified drivers, buses in poor repair, etc.. and are always being chased by the TSA. Keep an eye on flight discount sites, you can sometimes find great round trip deals to NYC for the weekend.
The Metro can take you everywhere... Also since your a gamer check out the Smithsonian Art Museum it happens to have an exhibit on video game art. All the Smithsonians
are free as well so if you are a nerd at all it is heaven. With DC they have way too many decent restaurants to name them all (it is best to ask what is your favorite food).
Whenever you go anywhere though check and see if Man vs Food
has a show on it and if they do you GOTTA eat at those places though. The chili place is the best meal I have personally had in DC.
If you like baseball check out a nationals game those are always good and not that bad of a price same with the capitals.
As for the bus companies to use another is Megabus
the bus has free wifi for the ride.
DC is normally good on having a lot of music bands but avoid Verizon Center it is just too big (unless you enjoy that kinda show).
I tried to include some links to help you out. That is all I can think up off the top of my head.