Last update 23 November 2010
Many speed testers are based on the Ookla engine.
This provides a simple easy speed test - I quite like it on all the sites that use it. However if you are using certain firewall/anti-virus systems these can cause crazy results.
For example many people including myself can get results in the high 10s of thousands kbps. My connection speed is around 6000-7000kbps.
The two I know of at the moment are Kaspersky IS and Avira Premium IS, both of which I have used.
Don’t be tempted to disable these to get a true reading. Trojans and other attacks are around all the time. If you must, then ensure (on Windows systems) that you enable Windows firewall before disabling the other. Remember to swap them back afterwards.