From NASA's site for educators comes this "finder" tool for NASA K-12 Teaching Materials. From the site:

Looking for Classroom Materials?

NASA's Education Materials Finder will help teachers locate resources that can be used in the classroom. Users may search by keywords, grade level, product type and subject. With hundreds of publications and Web sites indexed, the finder is the best way to locate NASA educational resources.

Click HERE to link directly to the "finder," or HERE to find out more about NASA for Educators.