If you're a Capital Bikeshare rider, you probably have some ideas for where new stations should go, and they want to hear from you. They have a cool site where you can suggest or agree with other suggestions on new station locations.
I just used it and it takes a little bit to get used to (if you double click to zoom it thinks you're marking a spot) but once you get it, it's pretty handy. I voted for 14th and Otis, which is a fairly big gap between two stations, and also at Upshur and Rock Creek Church near Slash Run and the Old Soldiers' Home entrance, where 23 other people suggested a station -- that seems to be the most popular location near us.
Other folks suggested places like Georgia and Park and 11th and Girard and 11th, which seem like good gap-fillers. 14th and Irving also has a ton of requests but the system recently installed a new station there, which is a good sign!
You can suggest as many stations as you'd like, so get to it!