Gow (Gnu On Windows) is the lightweight alternative to Cygwin. It uses a convenient Windows installer that installs about 130 extremely useful open source UNIX applications compiled as native win32 binaries. It is designed to be as small as possible, about 10 MB, as opposed to Cygwin which can run well over 100 MB depending upon options.

130 command line utilities and counting. 10mb only.

Use this on a flash drive if your co-workers don't lock their computers - just drag an image onto the executable and it will set the image as a centered wallpaper, even on multiple monitors.

command line PDF manipulator