Markdown support in Google Plus
Richpost is an extension which allows you to read and write MarkDown in Google Plus. It relies on the post having a #richpost tag through which it then recognizes convertible posts.
It's still very much a work in progress and an open todo list can be found at the github repo (https://github.com/Swader/richpost) if you feel like contributing.
For a detailed writeup on how and why this was built, see the blog post: http://www.bitfalls.com/2013/09/markdown-support-in-google-plus-chrome.html