Google Labs has release "Page Speed" as part of the Webmaster Tools collection. My site scored a "D" rating, and I am sitting on a VERY fast server, and don't have a ton of traffic yet. Page Speed will spit out a list of what's making the page/site grind to a snail-like pace, and give you a nice list to give to your host to work on. This is an add-on for Firefox, and works within Firebug.
The results of the speed tests are very eye-opening...
