What version of InDesign are you using? 100% display changed in CS6, but the underlying differnce in what you see is Photoshop actually measures in pixels and can give you a 1:1 display correspondence between image and screen pixels. InDesign, on the other hand, is really a print layout tool that is being "expanded" for use in on-screen design. The internal measuring system is points, and ID actually doesn't have a clue what a pixel is. Instead, it pretends that all pixel-based layouts are at 72 ppi (there are 72 points per inch in modern layout systems) and you are calling points pixels.
Prior to CS6 the 100% view was pretty meaningless since there are no monitors that actually have a native resolution of 72 ppi these days and it could be quite divergent from reality if compared to a physical ruler. CS6 has new code for alternate layouts that allows you to see on your screen what your layout is going to look like in various mobil devices, and part of that code also queries your system to determine the pixel density of the display, and in theory this means that your 100% view should now match a physical ruler. It seems to work pretty well on at least some Macs, but not on Windows 7, though it may do better on XP.