Well, continuing the feeling that there's just too much stuff being done to link to let alone download and try is Taxomita.
"Taxomita is a web-based authoring application that lets you create distributed, hierarchical, faceted metadata, and use it to index any page on the web.
The distributed bit is what makes Taxomita different. It means you won't have to do all metadata work yourself, you will be able to create a cloud of metadata sources you trust. You can indicate your trust on a topic-level, so you can indicate you'd like to incorporate Joe's indexing on "accessibility" in your map, but you don't care for his indexing of "babes on the web". (or the other way round)."
In version 2 they plan to have controlled vocabularies and thesauri. Would be nice to create your own from your own corpus. They are using eXchangeable Faceted Metadata Language.