Periodic Table of the Internet
While the web services aren't grouped into the usual solid, liquid, gas, and synthetic categories, you do have search engines, internet tools, site ranking, aggregators, webcomics, productivity and so on.
Of course, any attempt to actually index the internet so that you can see the whole thing on one page is bound to fail. There are thousands of sites you may visit every day that aren't included. But it's fun to look at.
What are your favorite attempts to graphically represent the web?