A few suggestions:
1. Look for a brightness of 200nits or better. Most have this, but make sure
2. Look for a contrast ratio of 235:1 or better. A lot of good ones are 250:1, 300:1, or 400-450:1
3. Look for the kind of connector you need. I'd personally suggest something with both DVI and VGA. I've used both connectors on my 18.1" LCD and the DVI is definitely cleaner.
4. Most importantly, look for something with 40ms or lower reponse time!!! This is something widely overlooked, and some manufacturer's don't even publish it on the quick specs. You have to dig through the complete technical specifications to find. What a low response time does is it keeps the "ghosting" effect to a minimum. If you can find something below 40ms, you will not have the trailing image problem with games and video. Be careful of those that don't publish this number at all. A LOT of em are 50ms or above.
Also, it's important to realize that there's quite a bit of difference between LCD's, even of the same specs. There's really no substitute to going in to a store and viewing the LCD, ideally with the same connection as the one you plan to use. As long as you look for those minimum specs, getting above them doesn't seem to really make a huge difference (ie. 450:1 contrast ratio doesn't look remarkably better than 300:1).
I'm currently on a Compaq TFT8020. 200nits brightness, 300:1 contrast, DVI and VGA, 37ms response time.
TFT8020
I looked at the SGI 1600SW, NEC LCD1830, NEC LCD1810X, IBM T84 and 86 (both the analog and the digital ones), and a bunch of Sony's.