Font Management in OS X - lots of tips on managing fonts in various versions of OS X, and what to do about Apple's versions of Helvetica, etc.
Undoing Font Book - how to reset Font Book's cache.
FontNuke or Font Finagler- utilities to clear font caches in OS X.
SquidGuard is a URL redirector used to use blacklists with the proxysoftware Squid. There are two big advantages to squidguard: it is fast and it is free.
A disk usage analyzer with an ncurses interface, aimed to be run on a remote server where you don't have an entire gaphical setup, but have to do with a simple SSH connection. ncdu aims to be fast, simple and easy to use, and should be able to run in any minimal POSIX-like environment with ncurses installed.
WPKG is an automated software deployment, upgrade and removal program for Windows.
It can be used to push/pull software packages, such as Service Packs, hotfixes, or program installations from a central server (for example, Samba or Active Directory) to a number of workstations.
It can run as a service to install software in the background (silent install), without user interaction.
It can install MSI, InstallShield, PackagefortheWeb, Inno Setup, Nullsoft, other software installers or .exe packages, .bat and .cmd scripts and similar: no more repackaging to perform software installation.
WPKG is open source software.
opsi (Open PC Server Integration) the Open Source client management system
Vagrant is a tool for building complete development environments. With an easy-to-use workflow and focus on automation, Vagrant lowers development environment setup time, increases development/production parity, and makes the "works on my machine" excuse a relic of the past.