It is a great way to teach children (or anyone else) the art of navigation. It is fun and they learn more about the world as well. I have my kids do research on the places they hear about from other geocachers.

My favorite GPS is the Garmin GPSMap 60csx. It has a SIRFSTAR III GPS chip which is very sensitive, and you can load the topo maps into it.

I like to have hard copy maps and a compass for my kids. I will help them plot coordinates and I let them navigate to a final attack point, then I make them use a compass and azimuth.

http://www.geocaching.com/

This site has all of the info you will need to get started. Get a few finds under your belt and then place one.

Geocaching can be done in any terrain, urban or rural environments and all over the world. It is fun and educational; and it is not a video game!