"A folksonomy is a system of classification derived from the practice and method of collaboratively creating and managing tags to annotate and categorize content;[1][2] this practice is also known as collaborative tagging, social classification, social indexing, and social tagging.[citation needed] Folksonomy is a portmanteau of folk and taxonomy."
I use this site to tag and keep track of my personal reading but have also found it helpful to see what others have been reading on the same subject.
Once you register and identify the city in which you live, you will be alerted to local book related events. Very useful site.