When I first stumbled across The Post Rapture Post, I thought it was a joke. But sure enough, you can order lots of different messages to be delivered. USA Today has more. It seems that the entrepreneur behind the site has sold almost 30 times as many t-shirts as actually letters.
That is exactly the off-beat idea for a business with which I wish I could come up! Kudos for 1) originality, 2) addressing a perceived need from another perspective, and 3) having a humorous product to purchase.