"Measurement Lab (M-Lab) is an open, distributed server platform for researchers to deploy Internet measurement tools. The goal of M-Lab is to advance network research and empower the public with useful information about their broadband connections. By enhancing Internet transparency, M-Lab helps sustain a healthy, innovative Internet."
You can check their network tools now (Java required):
"Network Diagnostic Tool (NDT) provides a sophisticated speed and diagnostic test. An NDT test reports more than just the upload and download speeds -- it also attempts to determine what, if any, problems limited these speeds, differentiating between computer configuration and network infrastructure problems. While the diagnostic messages are most useful for expert users, they can also help novice users by allowing them to provide detailed trouble reports to their network administrator."
"Glasnost attempts to detect whether your Internet access provider is performing application-specific traffic shaping. Currently, you can test if your ISP is throttling or blocking BitTorrent. Tests for other applications will follow soon."
"NPAD diagnoses some of the common problems effecting the last network mile and end-users' systems. These are the most common causes of all performance problems on wide area network paths."
All very useful...