Github Gists are a simpler version of a Github Repository if you'd like to only share snippets of code rather than whole projects/ Github has a great language rendering engine, the extension provided in the filename specifies how it is rendered when saved. All of my documentation is written in markdown. For more information on the Markdown language see this Markdown Cheatsheet. I have also found these tools helpful:
Private gists do not require you to login to be viewed. What makes them private is that the urls are not indexed. So that means their no map/sitemap saying they exist (this is only kinda true. if you're logged into the account that created it, it is visible). The only why to see them is to have the original link.
Public Gists are indexed so search engines are aware of them and they are visable under the user github gists collections page viewable at https://gist.github.com/[user name here].
Wanna see revisions of this document in case I removed something to better format it and never got around to adding it back?
Use the revisions tab to see the history of this document.
Also, I use the comment section for my notes that I haven't yet implemented into this document, so it should be accurate information but may not be appropriately formatted.
press the "edit" button in the top left corner of this document
drag and drop into the text area (assuming you already pressed "edit")
For more information see https://help.github.com/articles/about-gists/