In this website you can find information about folksonomies, their strenghts and weaknesses, and Sem4Tags an approach to improve multilingual folksonomies using semantic web techniques. In addition, there is information about the developed demo software to associate tags with semantic entities.
Daniela Barbosa, who is the business development manager for Synaptica at Dow Jones Client Solutions has written a fabulous eBook explaining how to mix taxonomies built by professionals and folksonomies, which let users tag content as they see fit
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A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proc. First International Conference on Semantics And Digital Media Technology (SAMT), volume 4306 of Lecture Notes in Computer Science, page 56-70. Springer, (2006)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proceedings of the 3rd European Semantic Web Conference, volume 4011 of LNCS, page 411-426. Budva, Montenegro, Springer, (June 2006)
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M. Grahl, A. Hotho, and G. Stumme. 7th International Conference on Knowledge Management (I-KNOW '07), page 356-364. Graz, Austria, Know-Center, (September 2007)
C. Schmitz, A. Hotho, R. Jäschke, and G. Stumme. Data Science and Classification (Proc. IFCS 2006 Conference), page 261-270. Berlin/Heidelberg, Springer, (July 2006)Ljubljana.
B. Krause, C. Schmitz, A. Hotho, and G. Stumme. AIRWeb '08: Proceedings of the 4th international workshop on Adversarial information retrieval on the web, page 61--68. New York, NY, USA, ACM, (2008)
B. Krause, R. Jäschke, A. Hotho, and G. Stumme. HT '08: Proceedings of the nineteenth ACM conference on Hypertext and hypermedia, page 157--166. New York, NY, USA, ACM, (2008)