Test Website Speed @ Google Labs
A new tool by Google, Page Speed Online http://pagespeed.googlelabs.com/ let's you test your website's page load speed. It seems to be a much nicer and more extensive tool than others such as YSlow. I guess it will be included as part of Google's Webmaster Tools soon.
I ran a test on our sister site http://greentranslations.com/ and got a Page Speed Score of 92 (out of 100) with a few useful Low priority suggestions from Google with specificity regarding exactly what we can work on. Just awesome!