A brief note on two pages I refer to during severe weather, like the storms that rolled through the area on Monday night and Tuesday early morning that led to tornado damage in Manchester on the morning of June 23, 2015.
LightningMaps.org has a zoomable near real time map of lightning strikes. You can zoom and pan around looking at locations of lightning strikes, with a small (less than 10 seconds) delay. When everything lines up right you can see the lightning strike on your computer before you hear the thunder.
The LightningMaps data comes from the BlitzOrtung project, which has deployed a set of custom designed lightning detectors world wide. From their page:
"Blitzortung.org" is a lightning detection network for the location of electromagnetic discharges in the atmosphere (lightning discharges) based on the time of arrival (TOA) and time of group arrival (TOGA) method. It consists of several lightning receivers and one central processing server. The stations transmit their data in short time intervals over the Internet to our server. Every data sentence contains the precise time of arrival of the received lightning discharge impulse ("sferic") and the exact geographic position of the receiver. With this information from all stations the exact positions of the discharges are computed.
Blitzortung is working on a new generation of lightning detectors, which are not yet available, and they are no longer manufacturing their first generation of detectors. Even so the US coverage of lightning detection is very good and recommended for storm tracking.