Shade’s Larp List has set up a Frappr map as a way of creating a census of larpers around the world. You can see Shade’s introduction to the concept here: www.larplist.com
A Frappr map is based off Google Earth, and allows you to locate your position on a global map and see the location of everyone else who’s on the map.
The international larp Frappr map is here, check it out and add yourself: