Our first project in Photoshop CS5 this semester was called Oxymoron Project. I sent the students to the website oxymoronlist.com. From there they had to choose an appropriate oxymoron for inspiration for a photoshop project using 2 or more photos. This project was used for practicing layers and the tools within Photoshop CS5.
Here is the instruction sheet and some student examples:
Oxymoron: Dead Alive
Oxymoron: Bird Dog
Oxymoron: Icy Hot