Pocket letters, have you tried them yet? They are becoming one of my favorite swaps. I really enjoy finding things to fill each little pocket. Sometimes I use things from my own stash, sometimes I make an element, and, then, sometimes I shop. This one the theme was "Something Wicked This Way Comes". I have a huge stash of Halloween so it was rather easy to fill. You can find more info on Pocket Letters HERE and HERE.
Have you participated in a pocket letter swap? If so, do you save your letter as is or use the items?