Git repository: http://git.dollyfish.net.nz/git/mutt-filters (browse)
A collection of filters to produce text/plain representations of commonly emailed formats (suitable for mutt's auto_view)
So the summary is a bit of a lie, it's really just one script so far :-)
You can get a copy of the raw script directly from here if that's all you're after.
As always, let me know if there's any bugs or if you have any cool ideas for improvements (ideally with patches).