I use this one:
http://infospeed.verizon.net/speedtest/speedtest500k.asp
It gives different results each time. I would give it more credability.
not me, it doesnt allow a choice in servers so you can test an average of your own. Besides I know that ones full of it, I used it and said I only have 750kbps, however just yesterday I downloaded a movie from movielink at 3500kbps.