The project, by the U.K.'s Oh Comely Magazine, costs about $1.50 to join (one pound, that is). They'll pair you with a stranger and you take it from there.
That means, you prepare a little box of stuff you like and send it. Hopefully, they'll do the same. And that's all there is to it. The pleasure is in the creative part of the giving and the surprise of the getting and, really, the whole non-digital, hands-on, imaginative process.