If you haven’t checked out xkcd.com, you should.  Not only is there a ton of extremely geeky humor on there, but every now and then he does the most amazing graphs.  Here is one he did about Online Communities, representing the amount of “action” going on in any community as continent size on a map.  It’s very easy to read, and shows some rather amazing things about social community usage (as of right now).  You can click on the image below to see a full-size version (necessary for the fine detail).