Pingdom – http://tools.pingdom.com/
GTmetrix – http://gtmetrix.com/
Gtmetrix gives you suggestions what you need to improve your website. Although Yslow and Google page speed are recommended for Firefox, it can also be applicable to other browser.
Load Impact – http://loadimpact.com/
Loadimpact is a very important tool for large Website visited by tens of thousands visitors each day. A free account allows you to check the loading impact with 50 simulated users.
Site Perf – http://site-perf.com/
Site-Perf fully emulates natural browser behavior downloading your page with all the images, CSS, JS and other files.
WebWait – http://webwait.com/
Benchmark your website or test the speed of your web connection.
Webslug – http://www.webslug.info/
Allows you to compare your website’s speed against your competitors.
Gives you the option to understand how your page is loading with different visitor’s Internet connection speeds.
iWebtool – http://www.iwebtool.com/speed_test
iWebtool gives you the option to compare up to ten pages in same time. You also can check homepage, categories or posts loading time with just one click.