Zoom Astronomy

From site:  Zoom Astronomy is a comprehensive on-line site about space and astronomy. It is designed for people of all ages and levels of comprehension. It has an easy-to-use structure that allows readers to start at a basic level on each topic and then to progress to much more advanced information as desired, simply by clicking on links.

AllAboutSpace.com (Zoom Astronomy) also includes printables, activities and worksheets.