I first of all recommend getting an LCD which is a given IMO, CRT's are pretty much on their way out and it's getting harder to find one. Go with an LCD because their easier on your eyes in my experience, they put off less heat, and they look good. I recommend acer for a cheap, and good brand of LCD's. You can get a 17" for under 200 bucks and I think you might even be able to pick up a 19" on sale for less than 200 bucks.
From what I've read, in a monitor you want a higher resolution. I recommend 1280X1024 for a 17" but higher is better because you'll get better quality. Also you want a monitor with a low response time, a response of about 4-8ms would be about average in a budget monitor and that's pretty good. Mine has 6 or 8 and I dont' notice any ghosting. Also one last thing to look for is the contrast ratio. some have a 350:1 ratio but I believe higher is better so look for a higher one.
Hope that helps!