How big are you looking? What kind of watching do you do? (Sports, movies, TV?) What are you going to connect to it?
Plasma/LCD argument is almost a religion, I'm not going to knock either. Just a heads up on some of their Strengths.
Plasma - Excellent black levels, more film like quality (positive or negative depending on your preferences), excellent off axis viewing.
LCD - Generally consider better for video gaming, can be thinner, lighter and use less power.
Both are excellent technologies you can't really go wrong with either. Also the strengths listed are just that. I'm not saying that because its a strength of one its a weakness of the other.
FYI - LED TV's are LCD TV's except the fluorescent backlight has been replace with LED's allowing them to be thinner and use less power. On higher end models it enables some pretty impressive features. (I don't know your background, I'm not trying to talk down to anyone. Just covering the basics)
HDMI - 1.4 is the latest standard, it supports full 3D and Ethernet over HDMI (it lets you use web enabled features from TV among other things). Something you may want to check.
Hz 120, 240, 600 etc... - depending on the what kind of viewing you do this may or may not be valuable.
-For sports, people tend to like the high frame rates. TV is delivered to you in 30fps (Frames per second) Sports have really fast action, at normal speed, you can get some motion blur. The higher Hz TV's have a feature that allows a processor to interpolate images between frames. Ultimately, it tries to diminish or remove motion blur.
-For movies, depending on your movie player this could be important. Movies are recorded in 24fps. You can set a player to playback in 24fps mode. These kinds of TV's also have a feature that attempts to remove any "judder" that maybe caused by doing this. (the speeds are all divisible by 24 and 30 so they can interpolate TV (30fps) and movies played in 24fps more evenly than say a tv with 60Hz which isn't evenly divisible by 24)
-In both cases you have turn on the feature to take advantage of it. Some people don't like the way it looks other do. Those that don't typically describe it as "everything looks like a soap opera..." or "the picture looks too real, like a video game" Other people, love it. Check it out decide for yourself. The upside is if you do get a TV with this feature and you don't like it, you can just disable the feature.
All of the big names make excellent TV Samsung, Sony, Panasonic, LG etc...
Samsung is making some killer high-end LCD/LED TVs
Panasonic makes some excellent plasmas
Vizio tends to make somewhat more budget conscious tv's. That doesn't mean they don't make good TVs, they tend to focus more on the mass market.
Just to throw this out there. There are a lot of people absolutely adore Pioneer's Kuros, line. The black levels are unreal. They are just a bit spendy and I don't think you can get one with HDMI 1.4
I hope this helps. Like everyone said, do your research to find a TV that fits your viewing style, space and budget.