In the past I toyed with the idea of sending HTML pages, including forms, via email, as the basis of a workflow system.
I never did anything with it because the target people all use Outlook and HTML support was always spotty, and with the latest version seems to be even worse.
Today I found out about Snap.
Snap delivers HTML forms for workflow purposes, but using RSS feeds. Your news reader becomes your task inbox. There is a demo available to see this in action.
I must admit that my head is buzzing with places where I really can use this. I see no reason not to do it in lots of places, and if I can get a decent windows-based RSS reader with HTML support (maybe FeedDemon, I'll have to check it out), then this has a lot of potential.
Also I can see other tools adopting this really fast. A "actions" feed for Trac tickets? Or Bugzilla bugs? Your personal todo manager?