In any event, let's get our kits together and plan to send them out by September 15 (I moved this out a bit since I was a little late getting the partners out; if you fail to participate or don't get around to this in a timely manner, you won't be invited back for the next swap, sorry....I hate to see disappointed children). The basic guidelines are to put together some sort of an age-appropriate mail/stationery set. For older children you'll likely want to send a functional set that one would use to write letters with, while younger children may prefer a set for pretend mail play. I'm thinking that you may want to send things valued at around $10-15, but that's sort of a shot in the dark, so you may wish to confer with your your partner so that you're on the same page.
Have a great time, and let me know if you have any questions! I can't wait!