I spent awhile last night looking at Elyse (no, not some beautiful woman, but a computer program). It is a tag-based file manager, with tag inheritance. For example, when you tag a file with "gazelle", it automatically gets tagged with "animal" too. Files can be stored inside the Elyse database, or Elyse can link to external files - in this respect it reminds me of UltraRecall.

This could be very useful in working with text note files. But I was disapponted to find that Elyse has no built-in previewer or editor for text files. Rather, to view or edit the file, you'd have to launch it in its associated program. Still - it might not be a huge deal to add a text previewer / editor? The program is under active development. The latest version was relased 4 days ago.

Another suggestion I would make to the author - for external files, store tags in "alternate data streams" of the files, so that the tags would travel with the files (on NTFS filesystems anyway).

http://silkwoodsoftware.com/index.html
http://silkwoodsoftware.com/screenshots.html
http://silkwoodsoftware.com/HelpFile/HelpFile.html (this can give you a good idea of how it works)