Aussie Internet speed checker
One the simplest looking (which actually is not a bad thing) internet speed tester website out on the net has to be testmynetspeed.com. They have a very simple design which makes it VERY easy to use. They have a chart right on the front page that shows you what different levels of service should be delivering.
The only issue for someone based in North America is that the service is based in Australia. But heck lets assume you are actually located in the region. I would recommend this internet speed checker to anyone who wants to monitor they service providers level of performance. I would bookmark the site and use it everyday.
But for someone in North AMerica I would say you can test it out but it might not be a great long term solution for a free internet speed check because the performance might suffer at times.