The book Good Mail Day (I love this book) is a great reference if you want to learn more about mail art and how to make it, how to find mail art friends to write to and much more. I've had my copy of this book on my worktable for a while and recently started making mail art. The cool thing about mail art is that Rule #1 - he/she who gets your mail art is supposed to write/send something back. What a great way to practice writing/letter writing and getting that surprise mail in your mailbox!
Here are some examples of some mail art that I made:
If you want to read my post about the above images, it's on my other blog, Intertwined and Inspired. I'll be writing a post about how to make your own mail art soon!