TagCloud is an automated Folksonomy tool. Essentially, TagCloud searches any number of RSS feeds you specify, extracts keywords from the content and lists them according to prevalence within the RSS feeds.
E. Rader, and R. Wash. CSCW '08: Proceedings of the ACM 2008 conference on Computer supported cooperative work, page 239--248. New York, NY, USA, ACM, (2008)