>>1778086Greyhound, Megabus, and Peter Pan tend to be cheap but their comfort level is dependent on the bus you're on. NYC to DC trips tend to be pretty good for that and for the many years I've made the trip, I've only had a serious problem about two or three times. Euro tourists and college students take these buses all the time and have no problem. You'll be fine and won't have to pay for parking.
One thing to keep in mind, check to see where the station is and what sort of transportation options are around. If you get dropped off at a suburban station, you might not have the ability to travel once you get to your destination. If you're traveling between two big cities, this usually isn't a problem.
