In term of the Monitor, the designers today still prefer to use CRT monitors, instead of the LCDs. Yah LCDs are cool, save space, and nice, but we, designers still prefer to work on CRT. (I think, pro photo editors would also prefer CRT instead of LCD.) For me, I have two 19" CRTs sitting on my table. But today, I've heard LCDs are getting better, but their prices are still too high for me. So CRTs are still cheaper and better option for me.
If youre into Professional, get the SPYDER Monitor Calibrator. Its important.
Relatively speaking RAM should be at least 512MB. (That is what I have on my system.), but of cos, the more the better. 1GB should be quite good, unless you want to edit large poster sized images.
And get a DVD-R/RW to backup your photos if your budget allows. Especially, if you shoot a lot, you will need such a large library.
And Photoshop & Wacom tablet is a must.