For years I’ve been very unhappy with the MIME type/application association.
The Ubuntu guys did a spec  and came up with a not-so-pretty UI, so I hacked something together. The (not yet implemented) architecture is described under , a very first (failed) UI experiment can be found under  and the first serious proposal under . I really like it :).
 and  provide python scripts that should run flawlessly under Ubuntu Edgy. It turns out that script languages extremely simplifiy communication between developers and usability experts as both can run a script and there is no compilation hurdle.
Feedback appreciated, preferably on the usability list.
I still don’t have a concept how we can properly integrate URI handling with MIME type handling. Maybe it’s best to just set the HTML/email message MIME type handler when changing the URI handler (the latter is stored in GConf).