How popular is Northwestern Ski trip? Are there parties? What do students do?
Check out their website if you haven’t yet: http://www.nuskitrip.com/what-is-nu-ski-trip/
There, you can find a general overview of what they do, as well as short descriptions of what Ski Trippers did on previous trips (the latter on a different page on the same website).
Basically, its a lot of skiing and a lot of partying, based on what I have read on the website and heard from participants.
In addition to activities on the trip, a group of people from NU Ski Trip rent two houses off campus. Students live there, and they have parties throughout the year usually at least one night a week, usually more frequently.