GitHub Visualizer - Enter user/repo and see the project visually
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.
Gource - Gource is a software version control visualization tool.
JSter - JSter is a community-driven catalog of the most useful javascript libraries.
SyntaxDB - Easily look up programming syntax for multiple languages
GitSpo - Measure & engage your open-source community