I have done a lot of different things over the years, however, the primary ones at the time are: exercising (lifting, running, racquetball, etc), gaming (video, board, card), and reading. I am not into golf.
When I first moved to the area awhile ago, other than work, I met a lot of people through Volleys. It's too late to sign up for a season, however they usually have weekend tournaments. The next time they have a Mad Hatter tournament, you don't need a team to sign up--it's everyone for themselves and rotated around.
Otherwise I'd find a gym and get into a racquetball league. When I used to do leagues, the other players were always looking for people to play against outside of league matches.
Generally, if you have any sport interest, the local group or joining a league (city/company/gym/etc) will get you to meet a lot of people.
There also used to be a meetup for ISU alumni to get together. I've never done it and haven't heard anything about it lately, so hopefully someone here might know if there are any alumni or game watch meetups.