Contra dancing, flash mobs, group singing, and facebook birthdays. Doing the same thing as lots of others around you feels good it's own way, differently from most things we do. Watching a comedy in company where laughs compound. Gathering at a funeral to be together in grief. Feeling the words of a charismatic demagogue play the emotions of the crowd. While our thoughts don't actually merge with the group's [1] we move part of the way to being a single entity.

[1] The Tines in Vernor Vinge's A Fire Upon the Deep and Children of the Sky do this. I enjoyed both books a lot.