A lot of people find accomodation through letting agents. You have to be quick now because Tour Operators are looking for appartments for their staff from this time of year.
Here are some agents that do seasonal lettings:-
http://www.agenceaim.com/
http://www.latourimmobilierchamonix.com/
http://www.arve-immobilier.com/
http://www.alpes-chalets.com/
When I did a season in Cham we used an agence right by the Casino which always seemed to have some good places. Generally you can get small apartments that are maybe not well placed for holiday lets quite easily. We rented somewhere right by the Brevent but it was ground floor with no view of Mt Blanc which meant it was unappealing for tourists.
If you don’t mind sharing, which can cut costs and be fun too, you should see if you can hook up with some ski buddies, somewhere like Teton Gravity’s forum would be a good place to look.
http://tetongravity.com/