I went looking for a way to test my bandwidth after finding out so many sites like SpeedTest.net require Adobe Flash Player in order to function. Well I uninstalled Adobe Flash Player months ago and refuse to install again just to test my bandwidth, so I went looking around and found out about HTML5 Internet Speed Tests. I've tried several of them, some seem to work, others seem downright broken.
I also found this article on TechRepublic about the subject.