Benthic Invertebrates in Our Waters
The EPA provides excellent pictures and complete descriptions of many of the interesting creatures that are found at the bottom of our state's beautiful water bodies.
http://www.epa.gov/bioindicators/html/benthosclean.html

Kids in the Creek
Provides a wide variety of useful material including curriculum, sample questions, vocabulary, and follow-up activites.
http://www.bpa.gov/corporate/kr/ed/kidsinthecreek/curriculum.htm

Aquatic Macroinvertebrate Identification Key
This site provides an excellent key for identifying aquatic macroinvertebrates.
http://www.people.virginia.edu/~sos-iwla/Stream-Study/StreamStudyHomePage/StreamStudy.HTML

The Rivers Are Alive
This pdf provides identification sheets for your students as well as educational pre-visit and post-visit activities.
http://www.nps.gov/sacn/forteachers/upload/RAAcurriculum.pdf