Hello,
I bought a 42in tv last summer on a college budget so I will give you what knowledge I have.
First off, there is some hard truth to the phrase "you get what you pay for". If you want a TV of that size, you're going to make some concessions. A lot of the cheap TV's in that size range (as a rule of thumb) just won't have the image quality of their more expensive counterparts. Should you find one that does have a superb picture, it will probably come with limited features. For example, I found a really nice plasma, but part of the price tag was that it has a very limited set of input options.
Samsung's cheaper tv's are very nice looking. However, what I would recommend doing is research some Insignia models. Insignia, Best Buy's in-house brand, operates by buying out unused parts from the major brands (Samsung, LG, etc) and building Frankenstein tv's with them. Sometimes the results are terrible, but, in my case, I found a tv that I was very happy with. The particular Insignia I purchased is effectively a Samsung plasma tv with a different casing. It even says "Samsung TV" when you plug a Mac into it. The picture is gorgeous (other than some screen glare issues) and the built in speakers are surprisingly rich.
Once again, RESEARCH the particular tv models you are interested in. This goes especially for Insignia, but you should do the same for any tv you're looking at. The details on the box are basically worthless. The AVS forums are you best resource for this.
Happy Hunting!