According to the Wikipedia, "Amateur radio direction finding (ARDF, also known as radio orienteering and radiosport) is an amateur racing sport that combines radio direction finding with the map and compass skills of orienteering. It is a timed race in which individual competitors use a topographic map, a magnetic compass and radio direction finding apparatus to navigate through diverse wooded terrain while searching for radio transmitters. The rules of the sport and international competitions are organized by the International Amateur Radio Union."
There is an active group in the East Bay conducting Radio Direction Finding, aka Transmitter Hunting or Fox Hunting every month. The schedule and other information can be seen at http://www.rdf-sf.org/
If you want to join in on the fun, watch out for email announcements sent to the SBARAHAMS Yahoo Group. If you are new to RDF, you can request for riding along with other participants to get a hang of it. Later, you can compete for the first place !
Enjoy Fox-Hunting, Amateur Radio style... !