Atheist Nexus is my favorite networking site by far. I tried myspace a couple years back and abandoned it almost immediately. I checked out Facebook for the first time over the holiday weekend and I was not terribly pleased. I think that a specialized site is better for real dialogue than a general purpose social networking site. (Melody's Freethought Forum was my previous favorite, but it died after Beltway Atheists took off.) I also think that this site would be better than the meetup groups for substantive conversation, as opposed to announcements and news items.
I think I may begin posting items with serious intellectual content here rather than in the meetup groups. I intend to write a more detailed rationale and post it on the B.A. & VFR lists.