Even though you've almost got a month, you don't have enough time to see everything, so pick what you want to see now and plan ahead. Try and narow it down so you're not traversing all over the country, of if you must see it all, do it in a logical fashion. Living in a tourist town in california(Monterey), I'll often run into people who saw all of southern California yesterday, and will be seeing all of northern california the next day. Needless to say, they're not seeing much besides the great freeway system.

Traveling within the US is more dificult than europe, as the only place you can take trains is new england, essentialy. Airlines are your only alternative and they're not cheap. All the big cities have definite feelings to them, so read a bit about everywhere you're interested in and see if you'd enjoy the city.

For the space shuttle, there's a launch on july 19th. If you're a member of any astronomy clubs or science of any sort, see if you can get them to send you as a reporter for their newsletter. I know someone who has done this and you get much better treatment.

Matthew