The most amazing website you can visit these days: http://www.lightningmaps.org
You will be able to track all lightning struck in your neighborhood or in other parts of the world. In real time! You are even able to follow how the sound travels after the lightning struck.
This is really cool and the information is very useful for us who like biking in the summer but don't like get surprised by a thunder storm.
There are instruction on how you may contribute data to this project by having a "receiver": http://en.blitzortung.org/cover_your_area.php
The receiver unit constantly measures very low frequencies (VLF) in the range of 3 to 30 kHz. When the lightning discharges there is a "signal" sent on those low frequencies. By measuring the time this signal appear at different places the location of the discharge can be calculated (provided that enough receivers are able to pick up the signal).