A utility for Windows XP and Vista that makes it easy to reinstall your system because it hunts down and packages up every device driver installed on your system, zips them up, and asks you to save them off somewhere. After the reinstall, DriverMax will help you reinstall them.
A freeware utility which clones most any hard drive block by block to another device. Possibly crypto agnostic.
A short tutorial on how to properly mirror part of a website using GNU wget, without accidentally downloading the whole thing, or parts of other people's websites.
An open source hard disk cloning/bare metal backup and restoration system. Bootable CD or USB device. Drop it in, reboot, and duplicate or push hard disk images across the network.
A perl script that can retrieve the config files of a variety of network devices for administrative or auditing purposes.
An utility written in Python that connects to an account on an IMAP server, recursively downloads everything, and stores the messages as mbox files. Useful for migration from system to system.
A shell script which can be used to automate the backup of virtual machines running in a XenServer environment. It's specifically written for XenServer v5.5, and I think it'll run reasonably well on top of XenServer v6.1 (I THINK).
XowA does one thing and does it well: It lets you make a local backup of Wikipedia (probably any Mediawiki, really) to carry around with you or copy to removable media (like a USB key or DVD-ROMs) so you can give out copies and read it offline. Runs on Windows, Linux, and MacOSX. Portable - can be run from removable media. Even includes a search engine. Written in Java.
The more-or-less official file format for offline reading of Wikipedia. The full byte-by-byte description of ZIM archives can be found here. There is also a zimlib-git AUR package for Arch Linux.