Dell Utrasharp LCDs are quite nice. Their lower end ones are are okay, but not as good.
19" for $246
http://accessories.us.dell.com/sna/prod ... u=320-4568
They have widescreens as well, albiet not in the ultrasharp line until you go to 24" (and over $600). 20 and 22" panels in your budget though, at around $230 and $300.
The thing to keep in mind with LCDs is that there are only a handful of manufacturers out there actually making panels. Samsung tends to make some nice monitors, but their panels are wrapped in a lot of other brand's plastics/control boards too. I know they were what Dell used for a while at least, if not still.
If your computer supports DVI output, I'd suggest buying a monitor that has that input option. Also, second input options (many times a VGA port as well) that allows you to swap between multiple sources can be handy.