The best terrain close to grenoble is Les 7 Laux, it's 30mn from the university and has a great park plus awesome BC terrain (more than 3000ft vertical drop w/ very good lifts).
Season pass is like 450€ and the day pass is like 17€ on weekdays for students.
Resorts in less than 45mn from grenoble include Chamrousse (flat but can be fun), St Pierre de chratreuse, Col de Porte Snowpark (almost free and open two nights a week, 20mn from grenoble), Alpe du Grand Serre, Villard de Lans, etc.
In a one hour range you have Les 2 Alpes, La Grave, Alpe d'huez, Serre Chevalier. And a lot more in less than 2 hours drive (Tignes, Les Arcs/La Plagne, etc.).
Without car you'll always find people at the university going to les 7 laux or anywhere else, and buses to the biggest resorts (Alpe d'huez/2 alpes). skipass.com is your friend here
