Tagging App and Service

http://readwrite.com/2011/05/13/tagger#awesm=~oGEdZgcVxHLfN6
https://github.com/apresta/tagger
http://www.quora.com/What-are-the-best-APIs-for-auto-generating-relevant-tags-from-text-content
http://www.alchemyapi.com/developers/getting-started-guide/
http://viget.com/extend/tagging-text-automatically