I always find the best technical info in forums - particularly gardening and tech stuff. I love pinterest for the traffic it brings and I'm learning to love G+ :) Stumbleupon brings good traffic too, but I have no idea how to really interact there and my favorite (still) is facebook groups for interacting. I hate that facebook hides our updates from pages though -boo hiss. YOU?
facebook is my go to networking site. It's just so easy. I get the majority of my traffic from pinterest, but don't find myself using it unless I have a project in mind that requires some research. Google plus is greek to me. I tried, but I can barely navigate things.
I've always been a lover of forums. They are more intimate and you can learn so much since they tend to be geared for specific interests. We had planned a saltwater fish tank and I stalked a reefing forum for about 9 months! I learned so much.