Yahoo's Exceptional Performance team has put together a list of "13 rules for making web pages fast" and posted it on Yahoo's developer network. The list, which includes "Make fewer HTTP requests," "Use a content delivery network," and "Avoid redirects," should really help webmasters figure out what is slowing their site down.
As if that wasn't enough, the team just released a Firefox add-on which integrates on top of Firebug, a web development tool. This add-on will analyze any web page to check for how they comply with the 13 rules. Once your page is analyzed, it will give you a letter grade, just like in school, on how your website fared against the various rules.
Yahoo has really compiled a great resource for web developers and I think everyone should take advantage of it. So, give the list a read, grab the Firefox add-on and see how you can help those page load times out!YSlow Firefox Add-on (requires Firebug)