CRT, LCD & DLP Projectors are the most popular
There are three main types of video projectors, although realistically speaking only two are practical. The first type of video projector to be available was the Cathode Ray Tube projector (CRT). Images from a computer or a video source are projected onto a screen by means of three small tubes - one for each primary color. However, CRT projectors are very expensive (around $10,000) and extremely bulky too, due to the required length of the cathode ray tubes. Due to the colors being produced from a balance of three tubes, CRT projectors are very delicate. The tubes can easily be mis-aligned or damaged and if damage occurs to just one tube, then all three must be replaced. These extreme sizes and costs make CRT tubes entirely impractical.
The alternatives are LCD projectors and DLP Projectors (Digital Light Processing). DLP projectors are better suited to the demands of video projection but may be more expensive than LCD projectors as a general rule. The quality of CRT, LCD or DLP projectors is determined by a combination of the resolution and the brightness. The brightness is measured in ANSI lumens. A projector of around 4000 ANSI lumens will probably be bright enough to give a powerful performance even in a relatively bright room. If the ANSI lumen measurement is high enough, it might be possible to use the projector in a room with total daylight without sacrificing the clarity of the image.
The most common base-entry resolution is SVGA 800x600, and some projectors can be double this, running VXGA graphics in 1600x1200. The difference in price between VXGA and the step below, SXGA is considerable and you may not find the difference to be entirely worthwhile. If you are planning to run the video projector through a computer, it is important to try to match the resolution that your computer runs in to the resolution of the projector. For instance, if your computer runs in 1024x768, then you should try to buy a projector that does the same. This way you are guaranteed the clearest image possible as every pixel on the computer relates to a pixel through the projector.
What will it cost?
Prices of video projectors are still high, but they have been falling and are likely to fall considerably throughout the next year or two. You can pick up a good quality DLP projector for around $2000 now, and it is predicted that this will halve within a couple of years. If you look carefully, you can probably find relatively cheap projectors that produce good quality images but without some of the fancy features of the more expensive models. If all you're doing is watching movies, then you probably won't need features such as zooming, or wide angle lens capabilities, so don't waste the money on them.