Do you ever eat fish? If so, are you aware that many fisheries are unsustainable, that popular fish species have high incidence of contamination, and that while generally good for you, some sushi can give you heavy metals with your wasabi?
For years I've carried around a pocket sustainable seafood guide the Monterey Bay Aquarium publishes semi-annually. Now they've got a smartphone app for both iPhone and Android. No more printing it out on paper! W00t!