Here are some articles on folksonomy that I found in a reading list on the Indiana University School of Library and Information Science website.
Peterson, E. (2006). Beneath the metadata: some philosophical problems with folksonomy. D-Lib Magazine, 12(11).
Vander Wal, T. (2007). Folksonomy coinage and definition.
Quintarelli, E. (2005). Folksonomies: power to the people
Mathes, A. (2004). Folksonomies: cooperative classification and communication through shared metadata.
Golder, S. A. & Huberman, B. A. (2006). Usage patterns of collaborative tagging systems. Journal of Information Science, 32(2). 198-208.
Some more:
Campbell, D.G (2006) A phenomenological framework for the relationship between the semantic web and user-centred tagging systems (in 7th SIG/CR Classification Research Workshop, November 4, 2006)
Gy. M and Tonkin E (2006) Folksonomies: tidying up tags? D-Lib magazine 12 (1).
Pirolli, P and Card, S (1999) Information foraging. Psychological Review 106 (4) 643-675.