I like that MAKE contributor Steve Lodefink is suggesting you buy this “gargantuan lens” from American Science & Surplus (for $10.95) if for no other reason than it’s badasss and will look cool weighing down your desk. Or, you can kick it old school (optically-speaking) and build an opaque projector with it. What’s an opaque projector, you say? Ask an old person, anyone who went to school in the middle of the 20th century. It was a precursor to the overhead projector, which was a precursor to the video projector. It was commonly used to project (and enlarge) book art and other reference material onto walls and art media for tracing purposes. Stephen has a link to PDF plans for such a projector on his site. He plans to build one and document the effort.
Make an Opaque Projector – Link