GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
TreeSize - TreeSize tells you where precious disk space has gone to.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
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.