Student, South Eugene High School, Class of 2017,
At South, it seems to me that cross country, theater, and soccer are the most popular extracurricular. I know for sure that cross country is super popular; I'm not as sure about theater and soccer, but they seem pretty big to me.
As for what I would recommend, we have an awesome FIRST Robotics team (South Eugene Robotics Team, Team 2521), which I think is super fun to participate in and very instructive. I would also recommend our Animal Welfare Society, which is a small but growing club determined to protect animal welfare by fundraising and volunteering at school and in the community. I also think Oregon Battle of the Books is an underrated but extremely fun competition to do with one's friends.