At GW, we have 4-RIDE which is a school run van system that runs all over the GW campus as well as the surrounding neighborhood. Runs from 7pm to 7am 7 days a week. It won't take you to bars, but it will take you to the nearest intersection.
Excellent program, and students really use it (esp. since a cab in DC is expensive as hell!!), which minimizes drunk students stumbling around campus.
I just wish the wait when you call for it didn't take FOREVER on Friday and Saturday nights.