There are clubs on campus for pretty much whatever you can think of! And if it doesn't exist? You can create it. Everyone ends up having a friend or two on student council and they can answer all your questions about joining a club or creating one. The administration is always open to new clubs. There is a club for whatever nationality you are (French, Russian, Israel, Spanish..it goes on) or for whatever political association you decide to make (the people running them will also help you choose if you'd like to, you also don't have to have a political affiliation to join the political clubs). As for the dorms, they are cool. The RA's are always awesome! The main dorm is full of life and good times. I personally never keep my door locked and people come visit as they please. The RA's and housing administration are amazing people and make dorm living a great experience. I personally "pot lucked" my roommates my freshman year and they are now my best friends in the world. If roommate living isn't for you Stern also has single room dorming. All dorms except the single rooms have private bathrooms. As for sports (I personally don't play any) Stern and YU both have a ton of teams. Sports range from fencing to baseball to volleyball and basketball. From what I hear the teams are quite good. I've been to a basketball game and the crowd is loud and always cheering for their team. I've been to many different shabbatons on campus and they are always packed with fun and good times. The food is wonderful and the people are always friendly. They are generally student run so they know what you want in a shabbaton.
Many of the students are a part of the different sports teams offered at Yeshiva University.