PostCrossing is a cozy website in which you basically send postcards to other random users, whom you cannot choose: you can see their interests only after the website draws them for you. After your postcards arrive, the website will make other people draw you, but still in secret.
Lemme tell you - this stuff's fun. First of all, it requires you to develop some sort of patience, since things need a while to arrive. Moreover, it's always nice to get glimpses of other cultures and people in general, and a postcard lets you do just that.
Another aspect I like is that it is against the rules to ask for any kind of postcard: this would make it some weird website for collectors. Still, some users write very disheartening things such as "do NOT send me handmade cards", even though they're allowed by the website.. obviously, I would never waste time on doing something handmade for a person who would not appreciate it, I guess - but my point is, why? I would love to receive something knowing that someone who doesn't even know me put in the effort to make something by hand. I guess they're worried about receiving silly things such as a dot in the middle of a blank card, excused by the sender as abstract art?
Luckily, the community is generally good. No one is benefitting sums of money from this, other than postage services I guess - but stamps are a small price to pay for wonderful little surprises, imo. Plus there's almost a beneficial sense similar to that of a ritual in sitting down, grabbing your supplies and writing to whoever you need to write. It requires time, patience - I know it may sound weird, but it is to me a very similar feeling to handling and listening to records on a turntable.
Oh, and if you ever sign up I also suggest browsing the forum: I started postcard-penpalling with a couple of users and that, too, is a really nice experience; it brings something different to the table. Still, it doesn't beat the surprise of getting cards from completely unknown users!
Last but not least, I would love to exchange some postcards with smallweb users, in case anyone's interested. Feel free to shoot me an e-mail (email@example.com)!