Play Munzee - Similiar to Geocaching but requires players scan a QR Codes instead to validate find.
iCaching - iCaching is the all-in-one Geocache manager for the Mac.
Geocaching - Geocaching is the premier app for locating geocaches. This app is available for both the Android and iOS platforms, and it makes locating these popular hidden treasures easy and fun.
c:geo - c:geo is simple yet powerful unofficial geocaching client for Android devices.
FlagStack - You can deploy and capture (virtual) flags all over the world. Join the scavenger hunt and have fun!
GSAK (Geocaching Swiss Army Knife) - GSAK is the all in one Geocaching and waypoint management tool.