I 2nd the vote for monoprice. Although becareful, the gauge of wire used in some of their cables can be rather thin.
Vizio, Insignia, I wouldn't bother. Samsung has a great picture for the money, I'd personally get Sony as I feel it has more accurate color reproduction which is more noticeable in the black levels than Samsung. Panasonic also makes very good TVs but cost a bit more last time I checked.
Btw, I wrote those manufacture selections before researching further, so I feel even better about those choices now after reading a CNET review which lists the top 5 best HDTV and they all below to those 3 brands. But of course those were $2k and up models.
I'd get a Sony XBR series if you can, but for $300 my input probably isn't very useful to you.
I just took a look on Walmarts website. If you can increase your budget slightly, you can get a Sony Bravia LCD 32" for $378 or a Samsung 26" for $314. Others under your budget is a 32" Westinghouse for $278. I have a 24" Westinghouse LCD monitor for my PC, which cost me over $500, and the picture is awesome and can go brighter than you'd ever need. The 22" Sony bravia is about the same price as the westinghouse also.