ICTlogy

Wikipedia entry:

Social software refers to applications which facilitate virtual connection and collaboration between people on a network. It is sometimes described succinctly as "connection comes before content."

The term came into more common usage in late 2002, largely due to Clay Shirky who organized a "Social Software Summit" in November 2002, having started to use the term in April 2002. Shirky defines social software as "stuff that gets spammed" [1]

Some of the following tools or concepts might not be strictly related to social software, but they surely have appeared on my path to social software knowledge. All in all, I had to gather all this stuff in some way.

more: http://socialsoftware.weblogsinc.com/entry/9817137581524458/
more (history): http://www.lifewithalacrity.com/2004/10/tracing_the_evo.html
more (directory): http://thevirtualhandshake.com/directory
comparison: http://www.consultantcommons.org/node/239