ExpertGPS is the ultimate geocaching software for your Garmin eTrex 30 [USB]. ExpertGPS lets you map your Geocaching.com .loc files and GPX Pocket Queries over USGS topo maps, aerial photos, and worldwide street maps. See exactly where the cache lies, and draw the route you'll take to the geocache. Use ExpertGPS to download all of the geocaches and the routes you'll take to your GPS, and to print high-resolution maps to carry with you.
When you're back home, use ExpertGPS to view the tracklog from your Garmin eTrex 30 [USB] and see exactly where you've been. ExpertGPS works with all your favorite programs, like Google Earth, MapSource, and GSAK.