We've featured DIY projector screens before, but as far as DIY projects go they can still get a bit pricey. If you're got a nice, flat wall, you can use this method to create a great screen on the cheap.
to sit at home and watch slides of beautiful pieces of art and art history on a vintage or modern projector and screen is the ultimate luxury and one of my very big indulgences, loves, and ultimate passions :-) - Portable Projector Screen
Genius! The Backyard Movie Theater You Can Build in a Day