PostSecret
Amazingly addictive/powerful/etc site of nothing but homemade postcards. I wish I could post them all here. I remember, back in high school, reading Shakespeare and thinking that it was not possible to compress that many references and meaning into such a compact form as sonnets and plays. I feel a bit like that reading these too.
While I'm at it, I might as well give a free link to another site with way too much meaning packed into an impossible small space.