I'm on an email list for announcements of new NASA educational resources, and I got one today. I took a look at at the educational materials pages and was again reminded of what an amazing range of resources are available from NASA, mainly for classroom use, but also for general space education and interest.
I downloaded a few educator guides that caught my eye, each a 3-8 MB PDF file with many pages of classroom activity sheets and supporting material, all identified by teaching standards references and grade levels. Titles include "Rockets" (132 pages, K-12), "Suited for Spacewalking" (100 pages, 5-12), "Planetary Geology" (223 pages, 5-college), and one for my own professional field, "Optics" (98 pages, K-12). There are also a variety of posters, lithographs (like the Saturn sample here), and even bookmarks. Cool stuff.