its a little early in the year for this (ideal time is usually about october/november), but if you want a job in a hotel or bar or restaurant:
1. find somewhere you want to work (town / lift region) and go on the tourist office website job section:
e.g. Lech – Zürs
Kitzbühel
Saalbach
2. visit EURES website and search for a job in austria
EURES
in my experience sites like natives, seasonworkers.com, resortjobs.com etc all come up with the same 100's of results for working for the same 4 or 5 british tour operators (thompson, mark warner, espirit, crystal)
for ski guide/ instructor jobs apply direct to ski school/tour company.
also the odd chalet and a few tour companies advertise on the gum tree london overseas job section:
gumtree overseas jobs but again its probably a month or two too early for many of the adverts to come for the 09/10 season