- About GitHub Pages and Jekyll discusses at a high level how GitHub Pages works with Jekyll
- Customizing GitHub Pages should be your first stop when diagnosing an issue or when trying to go behind the stock Jekyll feature set. It covers custom domains, plugins for things like sitemaps, RSS feeds, and emojis
- Customizing CSS and HTML in your Jekyll theme from a GitHub perspective
- Assets discusses Jekyll's handling of CSS
- Minima is widely cited as a good Jekyll theme to study
- Cheatsheet from DevHints.i