If there is one Apache module you must have for your production server, it is
mod_pagespeed by Google. I don’t know everything that it does, but that the beauty of it; I don’t! Pagespeed does a massive amount of various methods to speed up your website such as caching, lossless compression for most types of media and other things I don’t know.
In short, it does everything that you should do automagically.
Where do I get it??
You may get the latest version at anytime here.
Are there any downsides?
None that you should feel unless if you a running an active development server as this is mostly for production servers and the aggressive caching will get in the way.
To clear it, follow this short guide.