So many choices and options
These days, most brands are pretty good but some good, reliable brands of flat panel monitors seem to be Apple, Viewsonic, Dell, and BenQ. They tend to have good resolutions, refresh rates and reliable color maintenance.
Personally, I have a 30" Apple Cinema HD Display and love it. It is by far the best monitor I have ever owned and never regretted spending more on it. The resolution made me drool when comparing it to others when I was looking for a monitor. It has maintained its calibration very well and what I see on the screen matches prints easily. I love the 30" size for monitor "real estate" especially when doing photo editing or having a number of things open together.
I also use a 19" BenQ monitor as my second monitor but it is mainly used for browser windows, itunes and adium because it's resolution and colors aren't nearly as reliable as the Apple. It has never calibrated quite as true as the Apple one.