Fucking good write-up dude. Gonna do this like Wikipedia and edit some minor stuff:
1) Sidecut: Far and away the most important spec. a ski has. Determines the shape of the turn a ski will make on edge. Smaller numbers make tighter turns, larger numbers make longer turns. Roughly, a ski with a radius is for big mountain or high speed GS riding. Skis with shorter running lengths (explained below) typically need a tigheter radius than a similar ski with a longer running length to perform the same due to the physics behind loading up the ski during a turn (think of a 2x4, the longer you make the distance between two fulcrums supporting the board, the easier it is to flex the board in the middle).
2) Rocker/Camber Profile: Besides sidecut, this has affected the skis I've ridden more than any other specification. It determines the skis slow speed performance/turn initiation on hardpack; and how well the ski handles chop, crud and powder- even more so than waist width to some extent. (There is no industry standard on how rocker is measured and reported to the consumer - but a very easy measurement can be achieved if you think of a ski on flat ground, unweighted.
Splay is defined as vertical height the tip rises from the snow,
Length is defined as flat horizontal distance from the contact point to the tip of the ski)
Blister Gear Review has a good guide to rocker and the variations in modern skis here
http://blistergearreview.com/articles/rocker-101
3) Flex: Basically determines the high speed stability of a ski and how fast you need to be moving to make a ski start to work. i.e. Stiffer skis are more stable but require more speed to arc, softer skis begin to work better at slower speeds and get on top of crud and powder better. (There is no standard on how flex is reported, which is not entirely absurd since you would need to get data from many points in a ski, and most measurements would not take into account characteristics of flex such as rebound, dampness, etc. )
4) Waist Width: Dictates how quick a ski goes from edge to edge. Wider waists are generally indicative of larger surface area, which provides better flotation in powder.
5) Core Center, aka "Recommended Mount": This measurement is given in cm and specifies how far back of true center (the middle of the ski if you used a tape measure) the midsole line will be. Generally, but not for all skis, this point should be simultaneously these three things: the thickest point of the core, the thinnest point of the sidecut, and the suggested midsole mounting line. Heavily influences the skis ability to ride switch vs. the skis tendency to float in pow. Not all manufacturers list this because consumers sometimes see this number and mount the ski that distance BACK from the recommended mount. Measure twice, mark with sharpie, mount only once.
6) Effective Edge: This is kind of the newest measurement. It used to be (before 2008ish) that effective edge was always roughly the length of the ski minus 30cm for a twin tip (15cm of tip, 15cm of tail). However, several skis have been released with early taper on both ends of the ski, hence making the amount of edge in use when the ski is carving significantly shorter. This measurement can be listed either as effective edge (e.g. 130cm of edge in the snow when arcing out turn) or as the amount of tip and tail taper (e.g. 35cm of tip taper and 20cm of tail taper). Effective edge will affect how much edge hold you have, how stable the ski is when carving and how long the ski will feel. (Some companies list these dimensions, some don't)
