Boing Boing hipped me to the Electronic Frontier Foundations's ISP Testing Tool "Switzerland".
It's particularly resonant that EFF released this just prior to the FCC fining Comcast for violating Net Neutrality. Now we all check to make sure that no one is given preferential treatment or being denied access. Citizen Law Enforcers Unite!
"Until now, there hasn't been a reliable way to tell if somebody -- a hacker, an ISP, corporate firewall, or the Great Firewall of China -- is modifying your Internet traffic en route."