Letterboxing--Containers?

My family is thinking about getting into Letterboxing .
So I'm looking for some inexpensive, waterproof/resistant, sturdy containers about the size of two paperback books stacked cover to cover. Also shouldn't be brightly colored. The inexpensive is to keep costs down but also to lessen the inclination of theft as these will be left in the woods.
Thanks for any help.
Also any input or experience with letterboxing would be welcome.

Have you looked into Geocaching which has taken its roots from letterboxing? There are many letterbox geocaches around. Visit geocaching.com

Retired ammo cans work well in the outdoors. They are water and animal proof. A 30 Cal. can is about the size you are looking for. Make sure you mark the can letterbox/geocache to avoid it from being mistaken for something else.

I believe that you will find many more geocaches than letterboxes in your area. Many geocachers sign the log book in the geocache with their own custom stamp.

Yea, I Geocache a lot. Old ammo boxes are by far the most popular container. Available at Army Surplus stores for ~$5 is all.

Go to www.geocaching.com to find out how many are in your area. Top left of the home screen, simply enter in your Zip code and it lists the coordinates of em all, logs, pictures, a map of the area... Very cool stuff.
Some geocaches take more to find. Such as coordinates to a area that then tells you where to go, or 900ft East from this point, and others you have to solve a riddle, or somehow get coordinates from a poem. Kinda interesting really.

Good luck at whichever you choose!

Cameron