Film is still not dead. Anybody who thinks so seems to have missed the introduction of Velvia 100 and the announcement of Provia 400X, the new Porta 800, and Fujichrome T64, as well as hasn't seen how cool a Polaroid wedding guestbook turns out.
Airport security started being important in the late sixties, after people discovered they could hijack a plane. In the early seventies, the FAA required all airlines to screen passengers and their carry-on baggage, usually with metal detectors for the people and X-rays for the baggage.
Ever since Flight 800 blew up in 1996, in what seemed at the time to be terrorist causes but is now generally regarded as being caused by a faulty fuel tank, aviation security has been on the rise. September 11th just added fuel to the fire. An ever-increasing collection of security measures has been created, to the point where it has become more of a security theater than enhanced security.
I remember when you just had to ask nicely to get something hand-checked, and people would stop, take a quick look, and hand it to you on the other side of the checkpoint. Now, any item you attempt to get through security is regarded as an attempt to breach security, so you need to provide a very good reason for something to be hand checked.
It's a well-known fact that even if you use a "film safe" x-ray machine, films with an ASA above 800 will be damaged. The manufacturers admit this. However, if you run even 100 ASA film through an X-ray machine several times, it will start to build up fog. Galen Rowell, in Mountain Light, mentions that National Geographic has some Kodachrome slides in their collection that have been damaged by X-ray machines.
The TSA has guidelines for which films must be hand-checked, and they are actually reasonably accommodating if the TSA staff at the gate knows about the rules. Notable exceptions are for "professional" films, film that has already been x-rayed a few times, and film over 800 ASA. Worst case scenario, you can always claim that you are going to push process your film, and there's no way they can check that.
I have heard some horror stories about TSA agents not knowing the policy and refusing to believe a printout from the TSA website. I have been lucky so far.
There are lead-lined bags, but they are only rated up to 1600 and are regarded by most as a gamble. I suspect that a lead capsule like they use to transport radioisotopes would work well, but it would weigh a ton.
The best trick is to keep everything unboxed and in a clear zip-lock bag and hand them the bag at the checkpoint. Tell them that it's professional film and high speed film and they will usually check the whole batch, even if there are some non-professional films
But what about leaving the country, especially when you don't speak the language?
Usually tourist boards mention that you can get all your favorite films in their country. However, even in America, you really have to hunt for the good film. The closest I was able to find to my sort of film was Kodak's Elite Chrome 100 Extra Color, which is supposedly very similar to one of my favorite films (Velvia 100), except I've never used it.
If you plan a trip to a big city, you might be able to find a camera store that deals with all kinds of film, but many films don't get sold in every country, so you may come up short.
I found that, in the big airports, enough people spoke enough English that they'd eventually understand that I wasn't going to put my film through. They don't always want to inspect cameras. I had to rewind a half-completed roll because they didn't want to check it. My biggest problem, actually, was that I had separated out the film into several smaller bags and forgot to collect one, which meant that some 3200 ASA film got run through the X-ray twice.
I question if large format and Polaroid film will travel very well. The TSA folks were quite happy to do a quick visual check of the film and swap it for explosive residues. One guy in Peru insisted on examining each and every roll, including the film leader. I have no doubt that boxes of Polaroid or Large Format film would be opened and the security guy would want to examine the film in such a way as to inadvertently ruin it. Remember, people haven't been using large format film for a very long time, so they don't even know what it looks like anymore.