robzilla - 8:32 am on May 22, 2011 (gmt 0)
If you can install stuff on your server then I recommend Googles Mod Pagespeed
If you have root access to a server, you're probably better off optimizing your sites manually to minimize any overhead otherwise caused by the mod. When I tried Mod_Pagespeed, it actually slowed down my site. YMMV, of course, so it's good that you tested and got great results, but you're likely to get even better results if you turn off the mod and optimize your site by hand; the speed optimization documents by Google and Yahoo! are a good starting point.