I've been doing a fair amount of research into the whole DIY projector scene and it does seem some very good results are possible. There's a huge amount of information from 2 main sites:
DIY LCD video Projector - Home Theater - DIY Projector Company (DPC)
Lumenlab | Qx - The world's best computer
Rather than just magnifing a TV with a Fresnel as some people claim works (it doesn't), the idea is to drastically increase the light intensity through a LCD pannel, narrow that light signal and then re-project through a triplet projection lens. This creates units possibily capable of native HD resolution (dependant on LCD pannel used) for less than a couple of hundred quid. Look at some peoples results, they look good to me.... whats more, i just found this on ebay...
DIY PROJECTOR LENSES- FRESNEL & PROJECTION TRIPLET LCD on eBay, also, Projectors, DVD Home Cinema, Consumer Electronics (end time 10-Feb-08 22:00:57 GMT)
Has anyone over here made a DIY projector or does anyone know any particular forums attoned to DIY projectors?