Just as I was looking at the Webmasters tool today I found a new FireFox add-on tool by Google called Page Speed. It helps you evaluate the performance of your web page and get suggestions to improve the speed/performance of your web page.
The below video gives you a quick overview of the tool which showcases some cool features, like javascript minify and others.
Another alternative to this is YSlow another FireFox add-on from Yahoo, to increase the performance of your webpage
Another great free resource for seeing your exact timing as well as testing your site from an external location is at webpagetest.org. It lets you run a free web test from a bunch of locations around the globe and also lets you see exactly what is going on from the perspective of a fully external user. You can drill down and see exactly what is going on for each and every element being transferred.
Thanks for posting. The tool works great.