Something that I do every year in my Environmental Science class is discuss ecological footprints.  This starts the kids in my class with the mindset that what they do each day really does have an impact on the environment.  The one activity that they like the most in this discussion is the ecological footprint quiz.  This quiz asks you about ten to fifteen questions, of which you can provide vague or detailed answers, and then gives you an idea of the impact you have on the environment.  Kids love it and its simple and fun.  Try it out!