Paul Lorentz has a good article on how shaped skis use bending to shape the turn: Ski Bending
Paul has produced one of my most favorite skiing videos on Youtube:
Enjoy - there are a few more interesting articles on his website as well.
As to the energy stored in a bent ski, here is some hands-on experimenting:
Whether the ski itself is acting like a "trampoline" or is it mostly an effect of vaulting, there is much debate still.
This is more experimenting:
The consensus appears to be though that, although there is lots of energy in the ski itself, there is much more to be had by "vaulting" the body over the edges of the skis, from the forces of the turn.
Basically, as the skis turn across the direction of travel, towards the bottom of the turn, a lot of pressure develops, which we can use to generate and/or change the Impulse. We can think of it as a trampoline, but the energy powering it comes from the turn itself rather than your efforts (as would be say hopping), at the expert levels.
Also, here is a very good demonstration and discussion of ski bending at different angles:
Let's do some quick logic exercise, around bending a ski...