Minify
is a PHP5 app that can combine multiple CSS or Javascript files,
compress their contents (i.e. removal of unnecessary
whitespace/comments), and serve the results with HTTP encoding
(gzip/deflate) and headers that allow optimal client-side caching.

Yahoo’s Combo Handler and Google’s AJAX Libraries API both serve content from their heavy-duty CDNs and potentially
increase the chance that your visitor will already have a file in her
browser cache. Neither service serves custom content that you provide.
You may wish to use these services to serve popular libraries and
Minify to serve your code.
Minify is distributed under the New BSD License, which means that
you’re free to use, modify, and redistribute Minify or derivative works
thereof, even for commercial purposes, as long as you comply with a few
simple requirements. See the License file for details.

Requirements: -
Demo: http://code.google.com/p/minify/
License: New BSD License