The number of blogs in the world is currently upwards of 27 million.  A recent article by Stuart Luman discovered how they relate to one another.  They took the top 50 most-linked-to sites and mapped their connections.  See the linkage in the picture below.  The arrows represent links made sometime in the past 90 or so days - links that are in effect a global popularity contest.  Many of the blogs vote for each other which has been dubbed "blogrolling".  For more on this check out Stuart Luman's article titled Linkology.