Although Pre-Paid film mailers are not as common as before they are still sold. I love to use them when I am traveling. I shoot a roll, drop it in the mail. It usually takes a week so on a longer trip I return home to find my first rolls waiting for me. They are available from A&I or Fuji (Unique photo has them).
See
http://store.uniquephoto.com/e/index...600006359.html