The other day in a class, I found us throwing back and forth a lot of theory. I don't think it was intentional; we were all just trying to grapple with a phenomenon ("Why do people blog"?) and wanted to find sets of reasonable explanations.
This isn't the full list of theories that people like to use in CSCW. But it's a fair chunk of the dominant CMC (that's "Computer Mediated Communication") theories. I think it's useful (for me!) to keep around.