What is the best way to minify drupal's aggregated javascript (automatically)? Have just run Google pagespeed over my newly created drupal 6 site, and it reports:

Minifying the following JavaScript resources could reduce their size by 15.6KiB (12% reduction).

    Minifying http://[sites]/sites/default/files/js/js_9f19b87ffb72ca233ea7e45dda2f20f9.js could save 15.3KiB (18% reduction). See optimized version or Save as.


The above file was generated through drupal's default JavaScript aggregation method, but apparently it could be 18% smaller (which is a big deal for this site). What approach is considered the best when it comes to minifying JavaScript on a drupal site without breaking any existing code?
I created a new module to tackle a lot of the aggregation issue &amp; I hope to get a large chunk of it into D8; and yes it's a D6 module: http://drupal.org/project/advagg. Uses the jsmin+ lib for compression of JS and the CSSTidy lib for CSS compression. Main advantage of this is the css/js aggregate file doesn't change names unless it needs to; these files also have a 1 year cache lifetime &amp; has imagecache generation so 404s to your CSS file should be a thing of the past.

Update: AdvAgg 7.x is being developed and comes with minification of JS as an optional sub module. Other D7 options:
http://drupal.org/project/speedy
http://drupal.org/project/uglifyjs