Sample Projects your class can join right away:

Down the Drain: How much water do you use? Project
http://www.k12science.org/curriculum/drainproj/

The Global Water Sampling Project
http://www.k12science.org/curriculum/waterproj/

A great software tool for brainstorming, semantic mapping, creating papers... anything to inspire your kids!

Inspiration!
http://www.inspiration.com