What are the most popular student activities/groups?
There are some big organizations on campus such as Illini Pride and Orange Krush. These are student organizations are centered around sports games like football and basketball, which a lot of people go to. These groups consist of thousands of members and help students get good deals on campus as far as sports tickets and sportswear go. Student groups at UofI are called RSOs (registered student organizations) and there are hundreds of them. Anything from fencing, to sports, to jam bands, to comedy groups, to debate teams, to chemistry fanatics (check out http://illinois.collegiatelink.net). I am involved in the Illini Racquetball Club team. We meet twice a meet for "Practice" where we play racquetball matches. We have tournaments once a month and get to travel to other schools nearby like Indiana, Purdue, and Bradley, as well as hosting our own tournament. I'm also a member of a fraternity. Greek life is the biggest in the nation at UofI, meaning about 6,000 students are in a fraternity or sorority. Being in a frat/sorority isn't necessarily important but it helps you meet a lot of people very quickly, although if your not in one you'll still be able to make friends no problem. Some of my best friends are not in my fraternity and I met them freshman year in my dorm. I had a great dorm freshman year. People on my floor left there doors open and a lot of us were friends. This isn't always the case but you'll find it is a lot of the time.
There is a big drinking holiday on campus called Unofficial St. Patrick's day. It's usually referred to as Unofficial for short. Basically people just get up early and drink all day. It never really gets out of hand but if your sober it's a weird experience walking down the street. Some people party like this all the time and some people don't at all. There are a lot of bars on campus and you only need to be 19 to get in (18 in Urbana). But besides that there is a lot to do on campus that doesn't involve drinking. The student union has a bowling alley and arcade inside. Chamapaign has a lot of great shopping, restaurants, theaters, and a mall.