There are several websites that focus on the environment that are useful for learning and teaching. The Victorian EPA (Environment Protection Authority) has an ecological footprint calculator and a greenhouse calculator, which students would find both interesting and shocking to use.

Meanwhile the US EPA Teaching Center has a collection of resources on:

• Air – acid rain, indoor air pollution, ozone, radon
• Climate Change
• Conservation – energy, environmental stewardship, natural resources, pollution prevention
• Ecosystems – ecology, endangered species, global warming, habitats, watersheds
• Human Health – drinking water, fish advisories, indoor air, lead, ozone depletion, pesticides, radon, smog
• Stewardship
• Waste & Recycling – garbage, household, hazardous & solid waste, landfills, superfund cleanups, trash
• Water– drinking water, ecosystems, lakes, oceans, rivers, water pollution, watersheds

And although obviously US orientated, there is plenty of material that is useful for Australian and other schools.