.NET slave have post Efficient stylesheet minification in C#. Which will reduce the size of the stylesheet file you are using. I just wrote an application to do the same.

Attaching the application and the source below.  You can select a css file and a new file (with _ added on the file name) will be created on the same folder. You need .Net framework to run this application. It seems to be better than the YUI Compressor

CSSSizeReducer-Application.rar (4.35 kb)

CSSSizeReducer-Source.rar (34.49 kb)