I’m on Facebook, but my profile is private and I generally only friend people who I actually know “in real life”.
My Twitter feed is also private, but send me a follow request if you want to keep up with me that way. Twitter is a personal back channel for me, so I do lots of silly commenting there about my life, my family, my kids, my dogs, and the occasional frustrating library patron.
I really love Google Reader and share a lot of interesting things from around the web that way.
I use Flickr for photos, but only sporadically.
I sometimes collect YouTube videos and maintain a channel there. I even posted a movie of my own, about library buildings.
I also love Pandora and maintain a radio station there.