I read a magazine article about things to do with your kids and one suggestion was Geocaching. Geocaching is a game played with a hand held GPS; it's like a treasure hunt. There are boxes of stuff- matchbox cars, key chains, etc. hidden all over the world. You use your GPS to find the box; when you find the cache, you take an item out of the box and leave a new item inside. Each box has a log book to tell about yourself, where you're from and your experience tracking down the cache.
The article I read said something like, "There are Geocaches hidden in every neighborhood in every city..." I'm thinking, "Yeah, right!" After entering our zip code on the Geocaching web site we found the nearest box was less than 1/4 mile from our house! My three year old loved the concept of the treasure hunt and loves her new racecar even more.
More info...
http://www.geocaching.com/