My junior has a list of colleges he is looking at. Like a lot of kids his age, he wants to connect socially when he goes to college. This might be a hard thing to judge, but I would love to hear if you think any of the colleges below do a particularly good or bad job at helping kids get their footing socially.
Wesleyan
Colgate
Hamilton
Northeastern
Holy Cross
Vermont
Union
Brandeis
Tufts
Clark
Bates
Boston College
Vassar
Syracuse
Cornell
Rochester
Richmond
Villanova
UNH
I’m sure there are probably small differences here and there, but honestly you’re going to find this at every college. To generalize, smaller schools in more rural areas tend to have more campus focused social events while city schools tend to be a bit more integrated with the surrounded area, but I think pretty much every student falls under the “connect socially when they go to college” tent. Hard to imagine what the student that wants to be all alone looks like 
Perhaps a better way to approach this question is to describe the preferences/environment your kid wants. Does he want a more competitive or collaborative environment? Large or small? Urban, rural, or suburban? What about gender ratios? Factors like those and any others your kid finds relevant.
Cornell does an amazing job with freshman orientation and has a wonderful club/activities “fair”.
I think most schools do a pretty good job though of welcoming their freshmen. As stated above, I’m not sure that will help narrow things down very much.
@PengsPhils thanks. I’m actually asking more about schools that do a good job of helping students make connections early on. I know some colleges have week long or multi-day smaller group trips. Or maybe others have really good RAs with good orientation programs.
That’s exactly what I’m saying is ubiquitous. For most any residential school they are going to have a mix of this. Most schools have orientation (often in the summer now) + a welcome week, a club fair, RA’s that host events in residence halls. I know Northeastern well, so using them as an example, they have every one of those things I listed. But so do most on this list. The reason I focused on fit is that the type of people present is far more likely to affect social success than the small differences in how orientation/club fairs/welcome week activities are done. You’ll find different groups of people at most colleges, but higher concentrations of people that you’re more likely to be friends with never hurts!
I know Bates has (in addition to the regular freshman orientation) small group student-led 4 day orientation trips and a required first year seminar program which combines a writing course with freshman advising (links below), but honestly I think just about every school does something to get kids oriented to college. What specifically each college does is a good thing to ask about on college tours.
https://www.bates.edu/orientation/aesop/
https://www.bates.edu/orientation/fys/
While my suggestion is are not on your list, I understand what OP is asking. As I had a kid at a college that did little to integrate freshman, (GaTech) and a kid at a school that did a LOT to integrate freshman, Case Western Reserve U.
Case Western Reserve University splits freshman into freshman housing with 4 different interest areas, called “Houses”. such as arts and music, service etc. then students are really likely to make friends with students similar to them. At Case, every freshman and sophomore takes three core reading and writing subjects, and those Core subjects get students into greater Cleveland as well.
Also all Case students get free transportation into the city on buses and trains as part of their student fees. The seminar classes at Case require some sort of project in Cleveland whether it be a community garden, or tutoring in math or some other type of engagement. Also all Case students are encouraged to visit the really fantastic fine arts museum, so they get plunged into city life right away, its all at their doorstep.
Case Western is academically very similar to U of Rochester on your list, but perhaps better at integrating freshman, and in a more interesting location, that is somewhat less cold than Rochester. Cleveland is on shallow Lake Erie, and gets much less snow than Rochester, or Syracuse or Ithaca, all on your list.
Although I see OP may love cold weather, as I read over his/her college list !
Hamilton offers orientation trips prior to the beginning of the first fall classes:
https://www.hamilton.edu/firstyear/orientation/trips/home
For a first-year integration of academic and residential experiences, students can elect REAL:
A current Hamilton sociology professor collaborated with a former student in research that produced How College Works. The book’s essential topic pertains to the importance of social experiences in collegiate success. Among key insights, the authors note “what really matters in college is who meets whom, and when.” Because of this connection, I’d expect Hamilton, as an institution, to have attuned to this insight.
I approach your question a different way with my own children. I tell them to “bloom where they are planted.” There are opportunities everywhere you go in life and it is up to you to seize them, do your best, make the best of every situation, and “go for it!” Every school from a community college to a large university will provide social opportunities. It is up to you to reach out and make it happen.
Rochester, which I usually characterize as a school that is pretty laid back in terms of “pushing” student involvement actually has a very good first-year orientation program. Orientation is a week long with lots of activities designed to get first-years involved with each other and the school in general. Certain housing (Sue B, parts of the “Quad,” and now Genesee) are reserved for first-years and have, in addition to RAs, upperclassmen who live on the floor and serve as D’Lions (sort of social directors) and Fellows (who provide academic and EC guidance). It makes for a good platform for launching their social and academic endeavors from then on. My daughter is a senior there now and many of the people who were on her floor as freshmen remain her best friends. Campus-wide service days and start-of-the-year festivals (Yellowjacket Weekend early in the semester and Mel Weekend slightly later) provide a good focus for fun and service before the academic work sets in on a more serious note. It was just the right amount of school spirit on both an institutional and individual level for my daughter who tends to be sort of introverted.
Forgot to add that Rochester also has a pre-orientation program (URFoot). A three-to-five day outdoor program immediately before orientation week that even my decidedly indoorsy kid enjoyed.