The Internet Weather Map™ (IWM) is a free service that maps latency on the Internet. As an Open Community project, it uses data from volunteers all over the world to feed back latency on the Internet into a central database. Then that data is aggregated, and displayed in table and map formats, allowing you to see how the fast sections of the Internet are running. While it practically not possible to map out every segment of the entire Internet, the IWM product traces hundreds of segments to give you an informed idea as to it's overall latency.
The Latency Map is the heart of the service, which displays a map of any delays on the Internet, as well as in a table format. While the table displays the slowest segments, the map only displays delays (latency over 300ms). The data on this tab will refresh every 60 seconds, so there is no need to re-load the page manually.
The Tools allows you get information on your domain name, including an MX Record Lookup, and some additional diagnostics.
View the map
Tip: If you have a spare monitor, the map screen makes an excellent reference tool to keep displayed at all times. If not, try using it on an iPhone.