To demand a vibrant nightlife from a town like Williamstown is just not realistic. Most students—even the ones who miss the options of big cities or are just not satisfied with the Williams way of life—realize that. However, there are a lot of campus entertainment options. Of course, this isn't really a substitute for city nightlife—that is a separate issue. A huge portion of the entertainment on campus is composed of stand-up comedy shows and a capella concerts—not exactly the events you can dance and socialize to—but they are options, nonetheless.
For a small town, there is a surprisingly large number of parties, and there seems to be at least a couple every night either organized by a student group or the administration. Other than that, there is a party every night of the week in one dorm or another. Student organizations have put a lot of effort into improving the social scene, but the most tangible results were a couple of concerts every couple of months with really good bands. Nevertheless, it is fair to say that there are enough parties one can go to on weekends when the a capella concerts are over.