Are you looking for a LCD or a CRT (like the old TV's or older monitors)?
Probably an LCD, so here's some things to look for: A fast response rate-- less than 9ms is good. A high contrast ratio is also good--2000:1 is better than 1000:1. Max resolution settings...the higher the better. Ensure that it's compatible with your current graphics card, meaning that if it's meant to run at 1440x900, then ensure that your graphics card can support 1440x900.
As for suggestions for monitors, I'll leave that up to you. My only advice is to buy a name brand one (doesn't have to be a top of the line name brand, just not one made by some company that you've never heard of before!). Also, be sure to see what kind of a warranty it comes with. Researching and reading about monitors that you want to purchase and then compairing them will allow you to make an educated decision when purchasing one. If it were me, I'd plan on spending between $150-$200 on a nice LCD monitor that will last me a while.
Hope this helps!
War produces veterans, wounded both physically and mentally. They have sacrificed for us.....and it is now our job to help these veterans, as they have already helped us in ways we will never know, in ways that we cannot fathom, and in ways that we take granted every day.