Plash is a system for sandboxing GNU/Linux programs. Plash's aim is to protect you from the programs you run by letting you run them with the minimum authority and privileges they need do do their job -- this is the Principle of Least Authority (POLA). P
MediaFork is a GPL’d, multiplatform, multithreaded DVD to MPEG-4 ripper/converter, available for Mac OS X, Linux, and Windows. It is based on the source code to HandBrake
Cygwin is a Linux-like environment for Windows - for sel ;-)