what should the ppi setting be in PSCS in order to achieve an image where each pixel of the image is represented by 1 pixel on the monitor?
My second question is...is that the definition of a 100% crop...that each pixel of the image is represented by one pixel on the monitor?
1. Your view setting in Photoshop has absolutely nothing to do with PPI. You can view any image at 100% regardless of its size or PPI setting.
2. Absolutely not. See #1. a "100% crop" simply means that you crop a section out of an image without up- or downsizing it; the number of pixels in the cropped section are the same before and after the crop. To do this with photoshop's crop tool, leave the PPI box blank, or you will be resizing as you crop and it won't be a 100% crop any more.
For web images, the only relevant image measurement is pixels. Inches or centimeters are totally irrelevant. Read http://www.visual-vacations.com/Photography/digital_dpi.htm
for more info.