i am wondering if there is a plugin out there that can make it possible for registered users of a blog to tag existing posts -- i am envisioning a set of controlled terms (i.e. a kind of taxonomy, something i offer to the user) and a free set where anybody can tag anything with any term, i.e. a folksonomy.
of course,it would be nice then to be able to display these tags in a cloud, get all posts of a certain tag etc etc.
if there is no plugin, is this something that can be done. how hard would it be to code?
any tips would be appreciated.