Postsecret is an amazing website that shows postcards people have sent in that have some personal secret. The cards can be quite artistic, and the secrets range from very personal and deep to funny but real to plain scary and horrible.
They only have a few cards on the site now. The archives are available in book form (which is beautifully done and a fun read/browse) as well as a travelling exhibit. A small gallery of old cards is also available here.
As a side note, I think it's neat when a blog makes the transition to the "real world" like this, but I hope the site doesn't become worthless like Belle de Jour did when she published her book Belle De Jour : Intimate Adventures of a London Call Girl. (Not safe for work, btw. Also, is it required that websites that move to book form take the title pattern, "[sitename]:[tagline]"? That's like the old Microsoft naming pattern "Microsoft [category name] for [platform name]". Lame.)
Anyway, it's worth a few minutes to check out. Anyone out there sent in a postcard?