The basics of geocaching require a hand-held GPS device and Internet access. Visiting and joining (for free!) http://www.geocaching.com/ will give you detailed descriptions and locations. Find a cache you'd like to hunt for, enter it into your GPS, then have fun searching. Each cache is different. Some contain a trinket you can take and ask you to leave one in its place. Some have a log to record the date you found it and your name and hometown. At any rate, geocaching looks to be a really fun and inexpensive adventure for your family. I can't wait until my growing family is all old enough to understand and enjoy the hunt!
If you've already begun your geocaching adventures, I'd love to hear your stories in the comments!