In addition to Locally Owned Websites local websites there are a whole bunch of websites designed to facilitate social interaction.

Some specifically targeted people in Davis. They are all gone now, but they once included the following:
  DavisCoeds  dead
  UCDavisParties.com  dead
  UDavisLife.com  dead

Others have users from all over the world:
  Facebook
  Livejournal
  Meetup
  MySpace
  Nextdoor
  http://www.orkut.com Orkut  Had a fairly large UCD community at one point.
  Xanga
  Blogger
  Flickr
  Twitter
  Instagram Snap photos and share them

These succeed to various degrees in their objective.
