XKCD is a very solid webcomic for anyone who likes physics jokes, sciences puns, and making fun of people who fanatically argue the difference between "nerds" and "geeks," I urge you to check it out. 

Below is a map of online communities.  Physicist turned xkcd comic creator, Randall Munroe apparently gathered data from google and other such sources in order to range the size needed for each community.

I'm a proud member of the blogosphere (located at the bottom left corner of the map).
I'm also a less proud tenant of the twitter continent, which looks surprisingly like Greenland...