I was semi-amazed recently at the ease with which I took in all those social media/networking/sharing services when I came across a really helpful, organized list in a Widget (of all things) in the Big City Theme by MNKYstudio.
He had organized some of the best websites and applications used for social networking by category in his Widget. I really appreciated his work. I didn’t realize it would only get me started.
I’ve added only a few services (LinkedIn, Scribd, Google+, etc.) in hopes of not overwhelming even myself. This is by no means a complete list of what’s out there. If you want to see the whole thing, there’s quite a conversation going on.