GSAK (Geocaching Swiss Army Knife)
GSAK is the all in one Geocaching and waypoint management tool, used by thousands of geocachers all over the world. GSAK comes with many features that allow you to send geocaches and waypoints to your GPSr/Smartphone, keep track of your finds, hides, FTFs & DNFs, generate various statistics as well as carry out thorough geocaching searches to find just what you need.
The Website: http://www.gsak.net/
Feel intimidated by the software? Check out this handy guide kindly provided by Stuart, or The Tares Clan: