I found a great website thanks to this Sierra Club article with tons of ideas and stories about how to get kids out and about: http://www.recreatingwithkids.com/. The site is geared towards more active outdoor sports. So, don't expect to find tips on what to do with your two-year-old at the park, but rather some fun ideas of what's going on in the world of hiking, biking, skiing, etc for kids that are a bit older.
The site is based on Eugene Buchanan's book, Outdoor Parents, Outdoor Kids: A Guide to Getting Your Kids Active in the Great Outdoors
I haven't read it yet, but like the website, so check it out.