I was going to say the Bar Review and Wine Mess folks, because they do something every single week, but in reality I guess Federalist Society does too.
I don't really think of Bar Review and Wine Mess as a student org, but I guess it is. Federalist Society probably had at least
one talk a week in the fall, and several times more than one. I'm not sure why that leads to the particular emoticon you used, though, because more talks = more free lunches.
ACS had a few really interesting talks as well in the fall. Most organizations don't have the funding that the Federalist Society does, so they're limited to only do one or a few talks per year, unless they combine funds with another org for a talk that might have overlapping interests.
LSA is also pretty active. They have weekly meetings, help fund events that are put on by other organizations, and plan several parties and get togethers throughout the year. The Chicago Law Foundation holds a big charity auction every January (this Thursday) and so I imagine they're pretty active throughout the year organizing it, but I don't know what they actually do day-to-day. They also make and sell Chicago Law apparel throughout the year.
Greenbooks is an environmentalist student and they have used textbook sales a few times a year. The Edmund Burke Society is a (sarcastic, over-the-top) conservative/libertarian debate society that holds 3-4 debates every quarter. Neighbors is a community service organization that does volunteer work at a lot of neighborhood schools that includes things like tutoring, organizing drama activities and moot court, and a big essay-writing workshop for high school seniors applying for scholarships.
In sum: a lot of organizations are really active, but what it means to be "active" looks different for every group.