Webmin - Webmin is a web-based interface for system administration for Unix.
StableBit DrivePool - State of the art, file based drive pooling software.
ClearOS - A very good alternative for Windows Server, for free
btrfs - Btrfs is a modern copy on write (CoW) filesystem for Linux aimed at implementing advanced features...
cPanel - With its first-class support and rich feature set, cPanel & WHM has been the web hosting industry's most reliable, intuitive control panel since 1997.
Greyhole - Greyhole is an application that uses Samba to create a storage pool of all your available hard drives, and allows you to create redundant copies of the files you store, in order to prevent data loss when part of your hardware fails.