I’ve been using minimizing tools on my Javascript files for quite some time now. Most notably YUI Compressor, and it does an awesome job for me. Excellent job minimizing Javascript as well as CSS files.
Recently I’ve give Closure Compiler a try at Javascript compression and have been pleased with the results so far. It not only minimizes and obfuscates files, but also compiles them as well.
The rewritten code it spits out is not suitable for human reading, so be sure you always keep an original of the source to be modified. I have typically been saving 24% off the original file size. That’s typically 2x the compression I’d get if I simply gzipped the file.
Very cool tool, try it out.