Dan Elwell's Broadband Speed Test
 

Dan Elwell's Broadband Speed Test is a downloadable utility that can test your Broadband connection, identify any areas of concern, monitor performance over time and generate diagnostics you can use to send to your ISP. It's the ultimate connection monitoring and benchmarking tool, and is great for those who want to diagnose connection problems or are simply curious about their performance.

http://www.broadbandspeedtest.net/