The Economist has an article on environmental monitoring. It's the citizen science idea though which makes it particularly compelling. It involves tools to help interested people in gathering information that scientists can later use - and get long term data across a wider range on the planet than any one or team of scientists could possibly get. It's also great in helping kids learn about science: proper collecting of data, investigation, watching things over time, even making hypotheses about the data that they get.
There are also interesting technical issues with how to enable easy collection, processing, storage and analysis of huge amounts of data, but that can wait until next time.