I am determined to become an expert on GitHub this year!
(My profile on Github: https://github.com/selfpublish)
A simple Javascript input form with a calculation:
https://selfpublish.github.io/kdp-spine/
Todo: Add gutter width based on these calcs:

Git basics: This has a basic overview of how git works.
Pro Git e-book (web): This is a thorough git reference, in HTML format.
Pro Git e-book (PDF): Same as the preceding link, in PDF form.
Learn Git course from Codecademy: Git tutorial from Codeacademy.
Try Git course from Code School on Pluralsight: Git tutorial from Code School on Pluralsight.
Git and Github course from Udacity: Git and Github tutorial from Udacity.
15-minute interactive primer: This is an online git tutorial. It exposes you to the basics of git.
Cheat sheets: A quick reference to common GitHub commands and workflows.
GitHub Guides: The home of GitHub documentation.
GitHub learning resources: Other useful GitHub resources.
GitHub training services: A listing of tutorials and training offerings from GitHub.
Glossary: A handy glossary of git and GitHub terms.
GitHub Student developer pack : Give students free access to the best developer tools.