We were looking for a obfuscator and compressor that fulfills certain requirements (for instance, good compression rate and possibility to integrate it in an automated build process). We did not find a solution that is suitable for our needs, so I developed an own obfuscator and compressor which is online available now and can also be downloaded for offline use under http://www.scriptmixer.com
Perhaps this tool is also helpful for some of you.
I also wanted an way of doing compressing JS during the build process. I use netbeans as my ide of choice and it uses Ant during the build process. Looking around I found that there was an ant task compatible with Yahoo's compressor.
So all I did was modify my project build ant task to include compressed JS and CSS files.