Not maintained any more. I cannot catch up with GitHub's layout changes
Demos: README.markdown, commit comments, issues, inbox reply.
WYSIWYM Markdown editor for github.com
Install github-markdown-preview.user.js
Tested on Firefox 3.5, Google Chrome 4, Opera 10, and Safari GreaseKit.
Like UserJS, but with autoupdate and nice icon.
Based on GFM showdown.js