Look into these things:
Contrast Ratio (Higher the better) 500:1 or higher preferred
Response Time (Lower the better) under 25ms preferred
Brightness (Higher the better) 260 cd/m2 or higher preferred
Viewing angle (higher the better) 160 or higher preferred
DVI-d is a MUST
Another important thing is, you can't just look at the specs. No name brand LCD with 500:1 contrast ratio and 16ms response time may not even compare to a name brand LCD with 350:1 contrast ratio and 25ms response time. You REALLY have to go to a store and compare the LCDs yourself. Make sure you play around with the monitor settings like contrast/brightness. Make sure they are using DVI instead of VGA.
Here are some LCD manufacturers you should look into:
Samsung, Viewsonic, NEC, Hyundai and Iiyama. I've tried many different LCDs at home, work, and at the university so let me know if you have any more questions. I wouldn't recommend Sony. I've had some pretty bad experiences with them. Dell also makes great LCD monitors but they just use either Samsung or LG screens.
Have fun shopping around for a new monitor. =)