The one I remember the most fondly was Chatabout. I left Bubblews to post there because I was fed up with the continual crashing of the site. Chatabout was such a friendly site, I made lots of friends there but we weren't allowed to talk about other earning sites so it was very general chat which I liked. The founder was Australian and was very active on the site but one day we tried to log in and it was just a big white page, no explanation, just completely disappeared overnight.
There are two networks called Mind (or Minds) and Webtalk. I joined and I've already left them. StumbleUpon was supposed to be social but when they switched to MIX, I gave up on that site too.