GitSpo - Measure & engage your open-source community
Gitstalk - Discover what your favorite GitHub users are up to
Devo - Devo delivers real-time operational & business value from analytics on streaming and historical data to operations.
Octoview - The missing preview feature for GitHub
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful