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
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.
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)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Informatik 2006 -- Informatik für Menschen. Band 2, volume P-94 of Lecture Notes in Informatics, Bonn, Gesellschaft für Informatik, (October 2006)Proc. Workshop on Applications of Semantic Technologies, Informatik 2006.