What size do you want?
Dell's standard 17" is only $299; for $50 more you can get the higher-end UltraSharp of the same size. The Planar monitors on Dell's site are all $300-$330. One of NEC's is only $315...
The best way to know what you want is to go to a store like CompUSA where you can find a lot of brands in one place, figure out what you like, and use www.pricegrabber.com to figure out the best price online. You can also look up models at www.epinions.com to find what's rated good and what's rated bad by consumers.
Do look at Dell online, though...I just now glanced at what they have for sale, and there are a lot of sub-$350 17" monitors.
You also might want to look at Dell Small Business. You don't have to be an actual business to qualify for the prices, and they are currently having a $75-off sale on their monitors - a 17" standard is $224 and a 17" UltraSharp is $274.
If you wanted a 19", the Dell standard is $100 through small business and is right now only $329, which is an EXCELLENT deal for a 19" LCD. Keep in mind, though, that the bigger the LCD, the more light emitted from the display. My boyfriend had a 19" LCD for awhile, and had to return it for a 17" because the light was simply too bright. 17" and 19" LCDs tend to have the same resolution (1280x1024), so unless you NEED bigger text and more light, I would go with a 17" if I were you.
I'd be more than happy to help you find something, but the biggest thing is what size you want. Also, do you care what color the casing is? LCDs are usually in beige, black, or silver casings. Do you want/need integrated speakers? The Dell UltraSharp models have four integrated USB 2.0 ports to serve as a USB hub, and the LCD itself rotates and tilts and all that (lower-end LCDs usually can't move as much).
Dell 17" UltrSSharp[=http//accessories.us.dell.com/sna/ProductDetail.aspx?sku=320-4042&c=us&l=en&cs=04&category_id=210&first=true&page=productlisting.aspx]Dell 17" UltrSSharp - $274 through Dell Small Business
Dell's online store would be a good place to get you started - they have an extensive list of brands and models available, and you can compare features to figure out what you want most.
If you REALLY don't care about size, you can get a 15", but they only have a 1024x768 resolution. If you plan on playing games with a lot of movement on the screen, you will hate yourself if you get a "budget" display with a slow response time. You want 15ms or less response time on an LCD if you plan on doing a lot of high-movement gaming, or else you'll have irritating ghosting issues on the screen.
If you live near a CompUSA, they have a 17" monitor on sale right now for $175 with $120 in rebates, but CompUSA rebates can be REALLY flaky (as in you never get your money).
You probably won't find a better price on a decent 17" LCD than that Dell one I linked you to, or the cheaper standard one for $250. It has most of the same specs as the UltraSharp, but it doesn't have the USB hub, and it doesn't rotate into portrait mode.
Hope that helps!