I forgot to mention this little hack. It will take you to a “random” Web location:
Unfortunately, it's dreadfully slow: it works by performing a Google search on a random word (by using the Google Web APIs) and then selecting a random result among the first fifty. Since the dictionary of words contains French and English words, it is strongly biased toward French and English pages. Also, since the use of the Google APIs is limited, it will not generate more than one URL every twenty minutes (beyond that, the same location is returned). But still, it was fun to write. (Source code available upon demand, and I will put it in the Public Domain.)
If you're looking for something better, URoulette exists. But I don't know how it works.