How do I choose a monitor for PS CS3

So I bought myself a Sony VAIO SZ - VGN-SZ79GN/C notebook. Its light portable and has a 13.3 screen. I bought it to use when I travel and my Dell 17" notebook has now passed on to my son.

The display is 13.3" Wide (WXGA: 1280 x 800) TFT colour display (Clear Bright LCD: White LED) and I would like to get a monitor to use for photoshopping work (CS3).

I think the monitor only needs to be about 20" as that is what I am used to.

What should I look for? Any recommendations?

I not a pro photographer so I don't need the top of the range and budget is a consideration.

Any advice greatfully accepted.

Thanks

Knowing a budget is a good place to start

If your on one you can not get better than a second hand Sony Trinitron Flat screen.
Cheap, and if you make sure it is in good condition, better than even the best of the best LCD's.

If your after an LCD, there are plenty of things to look out for, but there are far better people to tell you than me.
I personally think they still have a we way to go before they are an affordable option, as to get the best quality (equivalent to best CRT), you have to spend large amounts of money.

20" Formac 2010 great display for not a lot of money