PostCrossing

Postcard a Day has a link to PostCrossing.

The goal of this project is to allow people to receive postcards from all over the world, for free. Well, almost free! The main idea is that: if you send a postcard, you'll receive at least one back, from a random Postcrosser from somewhere in the world.

Postcard Collecting Group

Flickr: Written Postcards - A group interested in the postcards and especially the writing on the backs of them. Scan your postcard collection, front and back, then post them.

I like that they include the story behind the card by including the written notes on the back. It's been awhile since I collected postcards. I still have them, some are really quite old (old for a postcard). Next time I have a weekend to fritter away I will see if I can remember to scan some of them and show them off to this group. :)