Windows to the Universe is a wonderfully rich web site put together by the University Corporation for Atmospheric Research at the University of Michigan is not only a source for a wealth of astronomy information, but for a lot of general science with some social science and history as well. And content is still being added.
One of the more intriguing features for registered users (free) is the ability to create online journals. I as a teacher create an account and enter in one or more "classroom" names. My kids can then register to create their own journals linked to my "classroom."
Once they create a journal, they of course can type in their own text, plus they can browse the site to add graphics and links with as little as two clicks (the journal is restricted to links and images from that site only.) I can create a "public" journal for my kids to read, or an assignment for them to complete using their journals. You can even print them out to keep.