the lower end High Definition tv are rear projection, a lot of times the line of sight is limited and you have to sit center to enjoy it 100%, these tv's have a high risk of screen burn in, wich is when you leave something on the screen for a long time, like a video game on pause, when you change the channel that image will be permanently "burned" on the screen.
DLP tv use a microchip with thousands of micro panels that reflect light into a color wheel, because it uses light from the start they are usually brighter, and they don't get screen burn ins like the other
lcd is a liquid crystal display that gives you great picture and a really thin profile. like plasma, the only problem with plasma is that it uses thousands of gas pockets that intereact with each other to form color, after a few years these gas burn out and you have to buy a new tv.
some of the best technologies available right now are probably DLP, Lcos and the sony Wega technology. I wouldn't spend my money on plasma anymore, hope that helps
