The Virtual Human Body is a great web site that is literally a virtual tour of the human body. You can explore the Brain, Skeleton, Heart, and Digestive tract. Each part can be explored and manipulated and some sections even have narrated tours.
In some parts, as you move your mouse over certain parts of the system, notes and information will come up on the screen. I think that it would be suitable for grades 7-12.
I found it easy to use and a great resource for students.