Anyways, I've really enjoyed using my old Dell re-branded Sony Trinitron 21", and they are pretty cheap.
There are better IBM monitors out there with killer resolution, but I believe they are pretty expensive. However, I must say after using the Dell 2005FPW, the Trinitron has yet to be turned on.
Just make sure it's got a flat screen. I was given an old 21" for free without seeing it first. Turned out it had a rounded screen and even though it was only going to be used as a second screen on our old Sawtooth, we couldn't endure looking at it.
Plus the fact it took up half the room. Seemed to be twice the size of our 19" CRT.