In reply to skarabrae:
I suspect you'd be looking for something roughly 90-100mm at the waist or close to that at least (depending on if you want 'lighter touring' or 'downhill, soft-snow centered').
I expect you'll want a length of not less than 175, and probably not more than 185 (again, if you're not a great skier a shorter ski will be a bit more forgiving).
Pretty much all the usual suspects will have a backcountry ski in that bracket so it kind of depends on how much you want to spend, and if you like your skis light, heavy, flexible, stiff etc.
Have you thought about:
K2 - Wayback, Coomback, Sideshow
BD - Aspect, Verdict
Scott - Mission
Volkl - Mantra, Kendo
Black Crows - Camox
Atomic - Aspect? Drifter?
Hagan - lots but I'm not familiar with them - Daemon?
Dynastar - Cham87/97
Line - Chronic, Blend?
It's probably worth being honest about what kind of conditions they're likely to encounter. At your size and weight you probably want a length of about 185 for skiing powder, but a shorter ski is easier to learn with, and if you're not a great skier might be better for getting a few days practice in resort/on piste.