Here's an interesting way of measuring your website performance through distributed computing.

CycleTraders is a cooperative network of users that gather critical information about the status of each other's website. By running the client on your machine, you donate some of your computing time to measure the response time of other user's web pages. In return, your site is also timed by all the other users on the network, from a variety of locations and connections. This data can be analyzed to gauge response time from different geographical locations, at different connection speeds, and at different times of the day. All this is automated through a web interface and an email reporting system.

The service is completely free, so for a minimal amount of effort on your part, you receive a wealth of information about your website, in any format you wish. For more information about how the network works, refer to the frequently asked questions page.