I was reading about this website today. It is called Postsecret. The concept started as a social study where a guy handed out 1000s of postcards and asked people to send them back with a secret written on them. Initially he only got back about 100, but ultimately people started making their own and sending them on to him.
I had a look at it and it is a lot like postcards from forumosa.
The site is www.postsecret.blogspot.com