This particular exchange is hosted by Crochet Partners. Details of how the exchange works can be found here (and there's a great picture of an FGX afghan).
I joined in January and so far I've sent 2 squares:
This one went off to Florida, USA. (#71 from Leisure Arts "99 Granny Squares to Crochet")
And this one went all the way to Queensland, Australia! (designed by crochetroo)
And I've received this one:
I love the little rose motif. This one came from Queensland, but not from the same person I sent mine to.
This is the sort of thing I get excited about. If the thought of little bits of yarny love jetting around the globe excites you too then join up! I'd love to send you a square.