I like this one: http://speedtest.net/index.php
If you can, try to pick servers in each that are about same distance from you. Maybe compare nearest server with furtherest one. Please post your speed and latency in your next post.
I would make sure you're wireless internet connection is secure, because someone on the outside could be using your internet without your knowledge.
I would also bypass the router and hook the pc directly to the modem and see if you still have the problem.
If this does not solve it, call your ISP and ask them to clear your line. Just tell them your experiences internet problems.
Please post me the results of using the modem directly compared to behind a router.