Frequently (daily, or a couple times per day) - reddit/imgur (news, jokes, tech stuff, etc) - instagram (for the pics... though slowly losing interest due to the ads) - twitter (news, fake-news, and tech stuff) - HN (news) - telegram (various programming channels)
Regularly (once or twice a week) - linkedin - ello
Infrequently (once every week or two or three or...) - facebook (I hate it, but all my friends/family are there) - google+ (photography groups) - vimeo
Practically never (once a year... maybe) - pinterest - flickr (really just to remind myself it's still there) - tumblr