I came across this article by the Huffington Post called This Is What Your Belly Button Says About You. It's chockfull of information about what the shape of our belly buttons say about us, touches on a few people who do not have belly buttons (they were removed in surgeries; they are not aliens), and the ever-popular belly button lint. So take a few minutes to read some of those strange facts, if you like.
And if that's not enough, there's a book out called Re: Belly Button Lint by Brooke West. I have a feeling it's not entirely about navel fluff, but I found it interesting that there's a book with belly button lint in the title!