Social Media: What do you use?

[dragonscholar]

I've got a mixed relation with social media. I use LJ casually, I am in love with Linkedin, I use assorted feeds and groups, but I figure it's time to sit down and analyze the assorted social media options.

So besides LJ what do you use in social media? Meetup? Facebook? Something else? What's worth it - and what's easy to automate?