Here are several online services that will help you test your site speed. Want to know how fast your page loads, they'll tell you that and a lot more. These services all offer a free version, some offer paid options for monitoring and ongoing reporting.
Pingdom has a really clean, easy to use interface. The report shows your page’s load time in seconds and as well as a performance grade. Each report details the recommendations and shows you the affected elements along with explanation and resources to learn more.
GTMetrix offers scores from both Yslow and PageSpeed browser plugins. It’s nice to contrast, since each tool keys off of slightly different factors. Great for the more technical, you can download a very detailed report in pdf format.
WebPageTest offers lots of options before you even run the test. You can choose different browsers, and choose to test from different locations. This produces a report with more technical depth, it can be a lot to dive into.
Do you test your pages for speed? Which online tool do you like and why?