Valdez is perhaps the largest and most well known heliski area in Alaska. Located right on the Pacific ocean, super cold and dry air allows for skiing steep and deep powder in relatively stable conditions. The Chugach mountains provide excellent terrain. The weather can be awful, though. It's not all that unusual to have helicopters grounded for weeks at a time. Alaska can get very cold as well. Oh - and the halibot fish and chips in Valdez is awesome (check it out at the Pipeline bar and grill, and wash it down with a cold Alaskan Amber).
Valdez certainly is not the only area to heli-ski in Alaska. Haines (way to the south) and Tordrillo (west of Anchorage) also offer up a world of first class heli-skiing.