GitHub Visualizer - Enter user/repo and see the project visually
GitSpo - Measure & engage your open-source community
CodeFlower - CodeFlower visualizes source code repositories using an interactive tree.
Devo - Devo delivers real-time operational & business value from analytics on streaming and historical data to operations.
Gource - Gource is a software version control visualization tool.
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.