I just wrote a wrapper application for Yahoo’s excellent CSS and JS minifyer YUI Compressor.
YUI Compressor is a command-line tool that allows you to minify one .css or one .js file at a time, reducing the filesize (quite drammatically in some cases) and increasing the performance of your site for first-time visitors (repeat visitors will already have these files in their cache).
My application wraps the YUI Compressor in a visual GUI, shielding you from the command-line scaryness that would otherwise ensue (ok, CLI’s are nice and friendly once you’ve used them a few times, but a lot of non-developers shy away from them). To minify files you just select them in Windows Explorer and drag them into the application window. The application then spits the files out into a folder on your desktop.
This means that minifying files is much faster because you don’t have to type anything, and it also means that you can minify whole batches of files at once :D
I wrote the application using VB.NET so at this point it only runs on Windows machines.
Download the application installer. The installer features everything you need including the original YUI Compressor CLI application. If you have not used the CLI version (or other Java-based JAR apps) before you may need to add data to your Windows class path in order to make it work.
For more information, see the Yahoo documentation for YUI Compressor