Youth Xchange is produced by UNEP and UNESCO, and it has links to loads of educational resources aimed at young people. Topics include the environment, consumption, body image, nutrition, and much, much more. I haven’t nearly explored it all, but there is a lot of good stuff here. It is mostly profiles of people and organizations that are making a positive impact, as opposed to materials they they have developed themselves. They also have a downloadable guide that features some of the highlights.
If I were planning a unit on one of the issues covered by this website, I would definitely check out the links they suggest.