Check out the forums on www.geocaching.com - there you will find a whole bunch of GPS related stuff.
Also look at:
http://members.aol.com/_ht_a/marklent60544/myhomepage/Geocaching/markwellgcfaq.htm
Also look at:
http://members.aol.com/_ht_a/marklent60544/myhomepage/Geocaching/markwellgcfaq.htm