For those of you who have a really old portable TV laying around with nothing much to do other than sit around, you might want to consider making one of these DIY handheld portable projectors. This isn’t the world’s top-of-the-line projector but still could be a fun project. And plus I am sure you can apply the same theory/concepts for any other projector projects you are working on. (Also see the DIY iPod Nano Projector too for reference)
A variety of application domains (ranging from ubicomp, through augmented reality, all the way to roaming performance art) would benefit from a lightweight, portable, battery powered projection device that could be used to display computer graphics.