If you want to learn more about how fast your site loads, then you’ll want to check out a new feature from Google Webmaster Central. It’s appropriately (and a bit vanilla-y) called Site Performance and right now it’s an experimental feature.
It will measure the speed of your site and then make suggestions for a quicker load time.
The site speed stats are provided via aggregated data gathered from users who have the Google Toolbar installed – and have opted into enhanced features. Sites with low traffic levels won’t be able to use this feature because of the way data is collected.