Michelle M. Casey, Perry Kennard, and Bruce and have written a very nice virtual lab using trilobites as a model system for teaching middle school students about macroevolution. The lab has plenty of high quality images with detailed explanations, so it is appropriate for use at institutions that don’t have extensive fossil collections.
Check it out: Introduction to the Trilobites (posted on 10 December, 2014).
A key to the questions is available (on request).
You can also check out the undergraduate lab.