This isn't directly related to Paraguay or to exchange, but I think it's worth mentioning. Postcrossing is a project that's been around for a few years. Basically, you sign up with your address, and people will send you postcards from all over the world, provided that you also send out postcards to random people all over the world. I signed up about a month ago, and absolutely love it. So far, I've sent out postcards to Finland, Russia, Poland, Netherlands, Germany, Switzerland, Portugal, Spain, and China. I've also gotten postcards back already from different people in Poland, Germany, Portugal, Spain, and Finland.
Check it out, and sign up. Postcards are generally pretty cheap, and so is postage.