This page is currently a loose collection of notes, eventually to be assembled into a coherent whole about how improvements in technology has enabled people to collaborate with increasing effectiveness.
era of print
The printing press made it possible for printed knowledge to be distributed beyond the walls of closely-guarded monasteries and private libraries. It also made possible the newspaper, the broadsheet, and other ways of disseminating news. These weren't necessarily controlled by a central authority, but they weren't exactly interactive either.
Inexpensive reproduction of written materials made possible mailing lists and newsletters and groups with local chapters. The mailing lists became emailing lists, from which came MoveOn and its inheritors, which created web sites that were mostly auxiliary to their main activity.
Then there came the (dial-up) BBSs, which became newsgroups, which became online forums.
Then there came the wikis, which spawned Wikipedia and other reference sites. The wikis enabled new technologies like "semantic markup" which are still being used largely on an experimental level.
Then came the centralized social networks -- Facebook, Friendster, and many others lesser known.
Then there came the meet-up/events planning services, like meetup.com and Facebook's "events" feature.