A nice one that I came by. On this one you can look at different rock samples and see the the minerals making them up.
http://students.open.ac.uk/science/s276/VM/program/openlearn/index.html
A prewritten lab to go with it http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-1.1#
This one would be good for high school or different parts off it would be good at different levels.