If you have a valid concealed carry weapons permit in one state, there are other states that offer reciprocity. Somebody has put up a neat little generator here. You put in the state where you have a license to carry and it gives you a quick color-coded map of other states where you can take your hardware. It is possible for a civilian with permits in a couple of states, to travel from the east coast to the west, if you don't mind a crooked route, legally armed with a concealed handgun. And most states will allow you to get a licenses even if you aren't a resident, if you can fulfill the requirements for classes and such.
I don't see the national carry permit in the near future, but if you don't mind the time, money, and effort, you can cover most of the country via the net or snailmail. There are only a couple of states that refuse to issue completely. If you know somebody, you can even get one in California.