I'm facinated by tagging and FacetedNavigation using tags. Thus, I'm a big user of http://del.icio.us/mshook and I'm also facinated by http://flickr.com
My PersonalWiki uses DiamondWiki. However, I don't use the general NameValuePair? (name:value) mechanism that DiamondWiki implements. Instead, vitually all my MetaData uses t: as the name, and the MetaData mechanism devolves into tagging.
I don't see that there's much about tagging here, but I've found it to be a powerful OrganizingPrincipal?.
My chosen language is PythonLanguage, but I'm also very much intrigued by what can be done with MozillaFirefox, GreaseMonkey and JavaScript.
It appears to me that you can't do FacetedNavigation on using the CategoryCategory mechanism because there's no way to search for two or more categories (I may be wrong about that). So I'm trying to see if I might be able to do Faceted Navigation using GoogleSearch, recognizing that the navigation would not be up to date. So far it's just a crazy idea.