Teach.Genetics has a bunch of “Print and Go” pdf lessons on their site, but also have a really neat interactive page where you can look inside an animal cell. What’s really neat about this flash app is that you can move around a little, round window as you scan through the cell membrane. You can also take the membrane away to see everything inside the cell at once, but that takes away the challenge.
When you use the little window you have to piece together what everything inside the cell looks like by memory. For a student new to the parts of a cell this might be a bit of cognitive overload, but once your somewhat familiar with the pieces, this makes for an interesting challenge.
The Teach.Genetics site and materials are free for educational use.