The Pooch (a team from Lancaster University, UK) has an awesome project: a DIY mobile projector:
Due to the lack of suitable commercial projectors of this type, .:thePooch:. set about creating just such a device. Using simple and cheap off-the-shelf components, it is possible to achieve unexpectedly good results. There will obviously be resolution and brightness issues, as one would expect with any low power device. However the device developed is practical for a wide range of applications requiring small scale projections in suitably dark environments.
In this project (very kindly described on their website), they turn a handheld TV set (+ a magnifying glass + gun-like spotlight) into a mobile projector, with a great design:
