I'll supply my two cents. As people have already pointed out, there are several technologies to choose from. From oldest to newest, the list goes: CRT, LCD, DLP, LCOS (D-ILA). Others can correct me if they want. My observations:
CRT: Theoretically the best picture, but low lumens and calibration woes. Plus, replacing the tubes is expensive. A dated technology that is on its way out the door.
LCD: Terrible. This technology has the worst case of the "screen door effect", which refers to the phenomenon of having individual pixels surrounded by big ol' black lines. Plus, it's taken for granted that dead pixels are a given with this variety of projector. Ironically (or more like "pathetically"), the image can be improved by deliberately displaying it slightly out of focus.
DLP: Image can be good, but this technology comes in two flavors. Single-chip (a-la the Sharp 9000 that people will often recommend) and three-chip, the latter variety costing something like $30k+. The screen door effect is apparent, but considerably less so than with LCD. The deal breaker with this technology is the "rainbow" artifact, which only plagues the single-chip variety. I saw the Sharp 9000 in action a few weeks back. Without knowing specifically what to look for, it took me all of ten seconds to notice examples of the rainbow artifact. Frankly, it amazes me that the single-chip variety of this technology has survived as well as it has, with such a glaring issue.
LCOS: The newest of the four technologies and the one I have decided to pursue. What I like about it: Highest "fill factor" of all the digital projector technologies (this refers to the space between the pixels; less is preferable), dead pixels are all but unheard-of, no glaring display artifacts, no real risk of burn-in (unless the votages were improperly set at the factory.. a possibility I still have to figure out a method for ascertaining), highest resolutions among digital projectors. Basically, this technology has the others beat, and has the brightest future. The only drawback that leaps to mind is the current dearth of models which can output an accurate color temperature, decently bright ansi lumens, AND last longer than a pathetic 1000 hours per lamp.
Note: As you were likely to discover on your own but I'll save time by mentioning now, LCOS is the technology. "D-ILA" is just what JVC calls their LCOS stuff. Nonetheless, it may be important to know that the technology may differ at least slightly, between manufacturers. For example, the Hitachi 5500, which uses LCOS technology, has a crippling limitation because of the way they implemented it. One cannot give the Hitachi 5500 a video signal which corresponds exactly to its maximum resolution.
Anyway, my recommendation isn't anything along the lines of going out and seeing what you like. I have to flat-out recommend LCOS. Or more specifically, D-ILA (JVC's LCOS, remember), since the only good LCOS projectors (in my estimation) are all D-ILA.