GitHub Visualizer - Enter user/repo and see the project visually
GitKraken - The intuitive, fast, and beautiful cross-platform Git client.
SyntaxDB - Easily look up programming syntax for multiple languages
SourceTree - Mac and Windows client for Mercurial and Git.
Codeology - Open-source algorithm that visualizes GitHub projects
GitHub Desktop - GitHub Desktop is a seamless way to contribute to projects on GitHub and GitHub Enterprise.