Co-ment allows multiple people to work collaboratively on a document and
annotate and comment on specific sections. Useful if you are writing up
a proposal and want comments from the community on it. I think it is
useful to package it and run a instance on Fedora infrastructure for
Fedora related proposals. It is a pretty significant piece of software
since a variant of it was actually used by FSF to collaborate on writing
the GPLv3 license.
Source at http://www.co-ment.org/
If you want to see demos, take a look at some text samples at
Who is volunteering to package this one up?