Here's a site I tried out today:
Comcast, BellSouth/AT&T DSL, Embarq, TimeWarner, and other companies often brag about their broadband speeds in TV commercials. In fact, some will state they can guarantee certain speeds.
If you want to truly know how fast your broadband connection is, access SpeakEasy's Flash-based speed test program:
I had to do this today when I tested my broadband service. What I liked about it the most is that it gives you different geographical regions of the country to test your speed, and the fact that it has no pop up ads.
Geographical tests gives you a better idea of why you seem to have a slower connection when you connect to other web sites and you get fast connections on others.