As for locations to visit, I think everything as been pretty much covered, but I'll give you a little advice for transportation: Southwest has been suggested, which is good, but also checkout JetBlue and Frontier for cheaper airfare. Their destinations are limited, however. As for buses, if you need to take them, I HIGHLY advise that you avoid Greyhound at all cost. A four hour drive can turn into a thirteen hour drive. There aren't too many, if any other nationwide lines, but there are smaller regional lines that you could look into. These tend to be cheaper, quicker, and they feel safer.
"I'd rather do it and have it end up bad, than never do it and wish I had."