Semanlink is an RDF-based personal information management system. It’s a tagging system. You can tag files, bookmarks and text notes. Unlike most tagging systems, Semanlink lets you arrange tags into a concept hierarchy. It runs as a servlet.
There’s a web page for each tag, but it doesn’t only list tagged items, but also “subtags” and “supertags.”
It’s a del.icio.us on steroids. The UI is not yet quite streamlined enough for my taste, but it looks usable. It’s technologically simple – Jena memory model, file-based persistence – so it should be hackable. Quite cool.
I’d use it if it had del.icio.us import (or synchronization, preferably).