Google has released an Apache module which attempts to speed up web pages.

I am testing mod_pagespeed right now.

I have noticed two problems so far. I had to add this to /etc/apache2/mods-enabled/pagespeed.conf to enable the CSS on one of my Joomla sites to load properly:
# Disable problem filters
ModPagespeedDisableFilters extend_cache,combine_css
It looks like this could have significant benefits and significant risks. Tuning the filters could be long and testing could be arduous.