mmmm....i'm gonna take a shot here...if i make a mistake, go ahead and flame me [img]smile.gif[/img]
Foam core vs. wood core. Foam is obviously lighter than wood, so you get a lighter ski. Alot of womens skis are using microcellular foam cores. Dunno what that means, but yeah...X-scream W, Vertigo G1 20/20 to name a couple. In terms of skiing performance, i can't tell a difference between wood and foam. Foam supposedly breaks down quicker than wood, so you loose the snappiness of the ski faster. Wood's heavier. Got to admit though, some companies are using lighter woods for womens skis...K2 i think is one of those companies.
Fiberglass, Carbon Fiber, Titanium. All used to increase torsional rigidity. Examples are Head's XP 60, 80, and 100. 60's use a full fiberglass jacket around their core, 80 uses a full carbon jacket around their core, and 100 uses a full metal jacket. Torsionally rigid, and makes the ski snappier to an extent. Carbon Fiber supposedly works the best to promote a snappier ski.
Rubber is technically used as a vibration dampener. K2's mod elastomer, Rossi's dualtec, etc.
i'm probably way off...but that's ok [img]smile.gif[/img] someone will correct me [img]smile.gif[/img]