There are numerous extracurricular options at MIddlebury. Most students are involved in at least one (excluding athletics), and many do two or more. There's a group for nearly everything, and starting one up is easy if you can't find what you're looking for. I'm a member of the Middlebury Student Quakers, which is a fantastic community of intelligent, caring, and silly individuals. We meet in the Chaplain's house on Sundays and you should drop by for Silent Meeting and then not-silent hanging out! Sports games are not well-attended, except for Quidditch and ice hockey, the former because it's so fun to watch and the latter because our teams are really good. Theater is better attended, and the student productions that happen in the Hepburn Zoo are pretty high-caliber. The Otter Nonsense improv troupe is hilarious and their shows always sell out.
Middlebury has no Greek system, but don't let that fool you. Middlebury has five co-ed "social houses," four of which (the fifth being the sub-free house) serve the same purpose as frats. Three of these four are pretty shameless about this, so if it's beer pong and date rape you're after, never fear. The fourth is the Mill, the "alternative" social house that's home base to the campus population of hipsters. They throw parties that are just like the other houses' parties, but with better music, more fashionable clothing, and drugs. But honestly the difference is manifest more in the Mill members' collective sense of identity than their parties, which get just as boring as the other houses' just as quickly. Between them, the four social houses provide popular weekend outlets for many, and there are numerous open and private parties in suites and rooms on any given night as well.
Thursday-Saturday is alcohol time for most Middlebury students, who embrace "work hard play hard" like a creed. If you're not into that, however, there are plenty of options. Take a hike, build a fire, call for owls, dance sober, people-watch, go to a movie, hang out with friends, take a road trip, look up local ghost stories, whatever. Middlebury-sponsored alternatives to drinking tend to be lame, and Middlebury students tend to be uncreative, which leads many non-drinkers to boredom and then to drinking. In truth, there's no shortage of things to do, but not many people here seem willing to dream up more exciting Saturday night agendas than getting trashed, dancing like idiots, and hooking up with strangers. Speaking of which, dating isn't a thing that happens here. You're either celibate, or you're hooking up randomly or casually, or you're joined at the hip with a significant other. There are no in-betweens.
If I'm awake at 2 am on a Tuesday, I'm either doing homework or with my friends, watching that episode of the Tyra Banks Show where the popular girls and the loser girls switch identities. Classic.