One of the most positive social experiences I've had here was through the Customs program, which guides your living situation freshman year. All dorms have members of all classes in them, which I think is very beneficial for integrating between classes, but the frosh on each hall are grouped into a "customs group" with two or three sophomore "customs people" who guide you through the early weeks and provide support and friendship. This is a very helpful bonding process, and my best friends here are from my customs group. This isn't always the case, but it's an excellent support network nonetheless, along with Hall Advisers and other people in place to facilitate community within the residences. The dorms are awesome as well, by the way.
The student body makeup is very different I think from most schools. It's very different from my high school, for one thing, where there were "cliques" and defined social stratification. That doesn't exist at all at Bryn Mawr. There are different groups on campus, such as the Self-Government Association, South Asian Women, and different athletics that have a lot of members and sort of have their own subculture, but no group has any sort of superior status over another. I think this may be because for one thing, most Mawrtyrs were either nerds or cool nerds in high school, and also most people are involved in many different activities. For the most part, though, people just have a group of friends that they spend most of their time with.
Students themselves tend to be liberal, politically aware, and socially concerned. There are some conservative students on campus, but not many. Really the only type of person who would be completely out of place would be a homophobe or a Paris Hilton fan. Just about anyone else could find people like them and be comfortable here. To class, there are people who wear very high-class designer outfits, people who could be wearing their pajamas, and the majority in casual clothes. There are a lot of students from Pennsylvania and New Jersey, but at least 2/3 are from other states or international. There is a pretty high contingent of international students. Financially, the majority of students are well-off, and some are extremely well-off, but these distinctions are not really apparent, there are plenty of low- and middle-class students, and the college gives excellent financial aid. I myself am on almost full-tuition and fees need-based financial aid, and I've never felt particularly uncomfortable with that.