Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
CopyCoding - Machine learning and data science online community
Octoview - The missing preview feature for GitHub
Betterer - Improve your codebase, incrementally
Dyllo - A clean and simple way to view a Github user's information
CodeKeep - Codekeep lets you store and share bits of code and text with other users. Snippets can be organized into folders/labels for instant reuse.