TreeSize - TreeSize tells you where precious disk space has gone to.
GitHub Visualizer - Enter user/repo and see the project visually
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Commit Together by Github - Now add co-authors to your commits
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful