Luckily, there are several bills in congress right now that, if passed, would require any state that issues concealed carry permits (so, right now, all states except Illinois and Washington D.C.) to recognize a permit issued by any other state. Of course, you would have to follow the laws of the state you were travelling to (better have those reduced capacity mags if you go to California), but at least it would allow permit holders to protect themselves and their families if they travel (and not have to look at handgunlaw.us to decide where to travel). Basically, it'd work the same way as drivers licenses.
I don't want to turn this too political, but one of the bills was introduced into the Senate by two Democrats (only mentioning this because Dems traditionally are anti-anything like this). One is from Alaska, the other from West VA. Hopefully, sometime soon, we can get LEOSA for the masses.