When I was 18-20 I used to travel by Greyhound bus quite often - all over Michigan. It was great. No ID, just pay cash, sit in the back with a bottle of Boones Farm. They stop in every hodunk little town along the way. It was a good experience. Way better than flying.
I only did once and was horrified in many levels. The people were all kinds of shady, and the toilet had this blue chemical that was splashing around. The whole situation was too peasant for me.