Website: NASA Educator Materials

NASA has a nice selection of educator materials available online.  The guides are available in pdf format - individual activities can be printed, or a whole guide. 

I have not made it through the hundreds of activities, but I can say that I've found several great ideas in the Rockets Education Guide - specifically several ideas related to Newton's Laws.  Among other things, it includes directions for making your own Hero Engine and Newton Car.  Newton Cars are high on my list of projects, and when I get one made, I'll be sharing my experience.

Of course, NASA is also a great source of images, history and more.