Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
GitSpo - Measure & engage your open-source community
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Devo - Devo delivers real-time operational & business value from analytics on streaming and historical data to operations.
Zube - Project management for developers.
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.