I’m confident that, after the failures Google Wave and Google Buzz, it will be Google +.
For now I’m gonna say it’s Fluther if we can call it a social media site.

I like eons.com it’s for the over-40 set. They have a lot of different groups to join. Sometimes beliefnet.com

I like google buzz. The problem is, i think i’m the only one who uses it . But Facebook pretty much consumes my life haha

I like Plurk. Its a bit like twitter, only more interactive. Each post becomes the start of its own little chat thread and its much easier to follow replies than it is on twitter.

I do flickr too but only for Second-Life-related stuff. My RL art is on Deviantart.

I like most all that you listed (will check into the sites I’ve not heard of—thanks for sharing)
For work I like FB, Twitter, Delicious bookmarking, Good Reads great place to share book club reviews, You Tube for tutorials and behind the scene videos and Flickr to document and advertise everything.
Personal, I like all of the above and the Stumble Upon, Tumbler. I love the randomness of those sites :) I’m sporadically using Google Buzz (I like it I just forget to check it regularly) and Google Reader (is that considered social site if you star and share it on Buzz?)
Fluther is proving to be a new favorite and I’ve shared it a few times with patrons when trying to find some detailed help. I feel like I’ve found more help than I given…love this site!