"Blitzortung.org" is a lightning detection network for locating electromagnetic discharges in the atmosphere (lightning discharges) with VLF receivers based on the time of arrival (TOA) and time of group arrival (TOGA) method. We are a community of station operators who send their data to the computing servers, programmers who develop and/or implement algorithms for locating and visualizing of sferic positions, and people who assist in any way to keep the system running. There is no restriction on membership. All people who keep the network in operation are volunteers. There are no fees, terms and conditions, and no contracts. If a station stops pooling its data, the server stops providing the access to the raw data for the user of that station.
There's more, mostly unintelligible to those not versed in meteorology or electronics. But the map is tres cool, and you might want to bookmark it to pull up the next time you have a thunderstorm approaching. -via Metafilter