Here's our hosted version of Webmonkey's Browser Stopwatch, complete with a bookmarklet:
Drag and drop the bookmarklet on that page to your toolbar to test the load time of any page you're on, in any browser.
Now, before this gets every web developer's panties in a bunch, let us disclaim: this is not a definitive way to get perfect, unchanging load times and browser benchmarks. In fact, if you run the test on the same site several times you can get wildly different results.
As the authors at Webmonkey point out after they ran the tests on a few pages:
The winner of the Webmonkey.com test is unclear—all browsers fall well within a very loose margin of error. The winner of the Picasaweb.google.com test is pretty clearly Firefox 3. [...]Our tests also vary depending on connection speed, how the browser renders iframes, web server speeds and the amount of elements on the page. We found that the results and margin of error mirror what the end-user sees when they judge for themselves whether the browser is fast.
Still, it's fun to see how long it takes pages you frequent to finish drawing themselves and loading other elements in your browser of choice; in some cases, like the tests in which Lifehacker.com clocked in at over 7 seconds, it's more painful than fun. (If you've got any element-blocking extensions like Flashblock installed, chances are things are much speedier for you, too.)
Give the Browser Stopwatch a try in your favourite browsers and tell us how it goes.