I look for several things, personally. First, I look for a fast refresh rate. Monitors above maybe 12ms can have ghosting on more graphic-intensive work. I like to be between 4-7. Remember that when a ms rating is gtg, it's "gray to gray", so it may not be as fair as other tests. You also want to look at contrast, for a better picture quality. I don't go for less than 800:1, usually going at least 1000:1.
I like this one:
HP W2007 LCD Monitor reviews - CNET Reviews
HP makes really solid monitors, and this one not only performs quite well but it's aesthetically more pleasing than many other higher quality monitors.