There is a meme (perhaps started at xkcd) that says that following the first (non parenthetical) link on a wikipedia article, recursively, always leads to the article entitled "Philosophy." Someone built a widget online to test this. You can try out random wikipedia articles, and see them leading to Philosophy – it draws a tree. Here's a tree I made with some random articles using the "random" button.
[broken link! FIXME]
There are some caveats (naturally) to how this works – explained here (read the comments thread). I like the example of a circular set of articles (try "Exogeny" in the widget).
