Have students conduct research on how much water is used by the average person living in their community, state or country. They can present ways to research water consumption and use to the class. Furthermore, they could create graphical representations of water used versus water wasted for the locale. Take students to a local water plant or conservation society to interview representatives and specialists who work in this field for a primary research project.
When the holiday season rolls around, challenge students to come up with a type of holiday light display that does not use as much energy as traditional ones. You could also give students a homework assignment to walk around their house and list all of the devices that use energy. They can then present the types of energy used in their home, as well as ways to conserve that energy, to the rest of the class.
Bring students to a local zoo for a field trip and assign them one animal to research while they are there. The students should ask specialists about the endangerment of certain species and steps that are being taken in order to ensure that the animal does not become extinct. Another project idea is to assign each student an extinct species. They should research and explain why that species became extinct, as well as steps that should have been taken to prevent extinction.
You might allow students to work on independent studies throughout the course of the semester or the entire school year. They could work as individuals or in groups to come up with their own plan for conservation that they have to put into action. For younger students, the plan could be as simple as writing a list of classroom rules for saving energy. More advanced students may be engaged to start a community wide clean up of a local park.