This National Endowment for the Humanities funded tutorial is one of the best online today. If you are interested in learning how digital imaging works, from conversion to compression, this is the place to start.
Teaching with Digital Cameras can be fun and exciting. In fact, many teachers have found interesting ways to include digital photography in their classrooms by using them to create everything from seating charts to visual journals, to scientific catalogs.
For Elementary educators, you might find this site interesting:
And finally, you might want to look at this site: