I want to share a great tool that I read about on http://www.dailyblogtips.com/ http://www.webpagetest.org/ Plug in your site and there you go. I've used several other speed tests and this is my new favorite.
I have used this before, and it really is very very good. I particularly like the ability to run the tests from different geographical locations to be able to see how well your hosting is performing. The other one I sometimes use is the firefox page speed plugin.