Not unlike homebrew beer kits, DIY projector kits are an easy to make projectors in the comfort of your own home. Unlike homebrew beer kits, however, a bottle skunky self-made beer won't burn your house down if you make it wrong.
The folks at LumenLab are here to help. They have a full DIY kit, forums, and free instructions on creating your own HD projector for pennies. While it may require a degree in electronics and a underdeveloped fear of death, it seems like an interesting way to rock your own 120" screen.