This is a video projector that I built from an LCD computer monitor, a very bright metal halide light source, some lenses, and a bunch of other stuff. It is a LumenLab design (www.lumenlab.com) (Great site by the way...lots of info if you want to build your own and a bunch of nice people) I am very pleased with the results; it produces a very bright and clear picture.

LCD Monitor Viewsonic VG150 - $185
EYE Bulb - $40
Lumenlab Lense Kit - $65
MDF - $20
M59 Ballast - $10
Socket - $10
120mm 130cmf Fan - $5
NorPro - $15
Flashing - $5
Tempered Glass (from halogen fixture) - $15
Various parts: Nuts, Bolts, Screws, louvre etc. - $20

Total: $390 Excluding the tv-tuner, With N4 tv-tuner, various cables, and other parts I probably forgot to mention  ~$500