A screen with an IPS panel is the best for photo work (as in colour accuracy etc), but they are quite pricey. I believe the Apple Cinema Displays are IPS, aswell as higher end Eizo, NEC and Hazro monitors.
Next is a PVA or MVA panel, which offer good colours and are quite affordable, I currently have a BenQ FP241w 24" monitor which is excellent.
Finally, there are the cheapest TN panels, which are more suited to gaming due to fast response. They have poorer viewing angles and colour accuracy.
Obviously calibration will help if you have access to a hardware calibrator.