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