RCSSmin is a CSS minifier. The implementation is based on the semantics of the YUI compressor, but aiming for speed instead of maximum compression so that it can be used at runtime rather than during a preprocessing step. rCSSmin does syntactical compression only (removing spaces, comments, and possibly semicolons). It does not provide semantic compression (like removing empty blocks, collapsing redundant properties etc). It does, however, support various CSS hacks (by keeping them working as intended).
Gow (GNU On Windows) is a 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.