Geocaching.com
From GeoWiki
Geocaching.com was the first major Cache Listing Site and has the vast majority of caches listed on it. It is a for-profit site run by US corporation Groundspeak. This site lists most caches in Australia but is quite US-centric and politically correct. Basic access is free and there is fee-based membership for functions such as downloading caches in GPX format.
For a full history of Geocaching.com, see the History of Geocaching.