If you're an emacs user, definitely check out org mode. Or if you've wanted an excuse to check out emacs, org mode may be a reason for you to make the move.
I use org-mode (with vim). It's low effort and anyone can see what I plan to do and submit changes with a pull request, without needing access to something other than the repository.
It's insanely powerful but not for everybody.
http://orgmode.org