The x-ray scanners used by airports these days will not affect digital devices like cameras, laptops, cell phones, mp3 players, cell phones, memory cards, CDs, or floppy disks at all. Of course, I never pack my electronics in my checked bags, because the airport luggage handlers can be pretty rough with those bags, and anything fragile in checked bags could be damaged.
The x-ray scanners will affect undeveloped film, whether it has been exposed or not. The scanners used on checked bags will instantly ruin film of any speed, so NEVER PACK FILM OR DISPOSABLE CAMERAS IN CHECKED BAGS!
The scanners used at the security checkpoints are less powerful, so it takes either multiple exposures or longer exposures for them to damage film enough that you'd notice. X-ray damage to film is cumulative, and it also depends on film speed; 400ISO film can be ruined by 4 passes through the carry-on scanner, while 800ISO or 1600-ISO can be ruined by one pass.
Keep in mind, however, that a "pass" through the x-ray scanner doesn't hit every single object with exactly the same amount of x-ray radiation. TSA screeners will often stop the belt to get a longer look at a complicated bag, thus bombarding that bag, and any others nearby, with far more than the "normal" amount of x-rays. It's for this reason that I NEVER let my film go through the x-ray scanner.
Getting film or disposables through the airport is simple, but takes a little advance preparation. First, remove film and disposables from their outer cardboard packaging. Remove the inner celophace liner from disposables, but you can leave 35mm film in the plastic canisters if they are clear. Second, put your film and disposables into clear 1-gallon Ziploc bags, and pack them near the top of your carry-on bag (where you can get them out quickly and easily). Third, take the film bag out when you get to the metal detector and hand it to the TSA agent, asking politely to have it hand-inspected.
The screeners at BWI and MCO have never batted an eyelash when I asked to have my film hand-inspected, although one guy did ask me why I handed the bag to him through the metal detector (I explained that a metal detector uses magnetic fields, not x-rays, and magnetic fields are totally harmless to photographic film).
For more details on this subject, click the link to my web page that yellow stitch posted earlier in this thread.