I'd like to add to what nextlevelmp said. I work in the HT dept. at Best Buy right now and i've heard all kinds of myths and rumors about every kind of tv that is out right now.
Most newer plasmas have been tested for burn-in. It usually takes 48 hours of a single still picture to burn the image in. Even if there is some slight burn-in after hours and hours of a still image it usually goes away after a few minutes of a picture that is moving. And yes, the half-life on most newer plasmas are near 60,000 hours.
Speaking of burn-in, LCD's are also at risk to burn-in. Go into a best buy and check out some of their LCD tvs that are hooked up to computers and change the screen, you'll see the best buy "screen saver" burnt in. DLP has no chance for burn-in and if ur lookin for a big screen for less money/inch, it's a good choice.
To the person that said to go w/ a 37" CRT, they still have risk of burn-in, they weigh around 250 lbs, they take up a lot of space, you can see the "pixels" on them much easier than most other tvs, oh and they're still usually around $1500 US (sony).
If you can afford it, check out the 50" Sony SXRD projection. They're Sony's newest LCoS (Liquid Crystal on Silicon). This TV has a 1080 native resolution, higher than any other tv that we currently have at our best buy (including the pioneer plasma). I played my 360 on this Sony the first day that i had it. It was amazing. No "ghosting" or motion blur, bright, awesome picture, and the colors and contrast are damn near plasma quality.
So, I brought my 360 in again and hooked it up to a couple other tvs because I myself am lookin to get a new big screen. First I tried a 42" LG plasma, not to bad of a picture on this one, the blacks in the games were nice and dark. Then I tried the 42" Toshiba, the picture was nice, but the blacks were kind of hazy and there was slight color bleeding around the edges of characters and objects when looking around in COD 2.
After playin the 360 in the store for about 3 hours (it was my day off), I decided to go w/ the 50" Sony SXRD.
All in all, dont listen to all the rumors out there about plasmas, yes they can get burn-in, if you leave it on for 48 hours of a still picture. CRT's and LCD's can also get burn-in, but even those will take a long time for it to happen. DLP is the only type of tv that CANNOT get burn-in, and they are usually cheaper $$ per inch.
So, it really comes down to, what size you want, how much space do you want to save, and what picture quality you want.