Blowing off a bit of steam here… Both Amarok and Thunderbird support adding custom “tags” to the collection items (mail and music, contra-respectively).1 Which is lovely: tags let you apply non-hierarchical non-exclusive categories to your collection, which is a wonderfully flexible way of organising it.

But neither application lets you search/filter on tags.2 Of course the main point of a flexible non-hierarchical non-exclusive categorisation system would seem to be … looking things up in the categories? Apparently some folk think otherwise.

Notes:

  1. Amarok calls them “labels” because the word “tag” is generally used for MP3 metadata annotations, so by extension to all music metadata. [↪]
  2. Afaik. I just started using Thunderbird, so I might be missing something, although a quick google suggests not. The Amarok I’m using is 2.3.0 packaged for Ubuntu Lucid, and I can imagine that a bleeding-edge version might have this added. [↪]