As far as Im concerns Sofurry and Furaffinity are the most interactive communities. Ive been a Sofurry member even before when it was Yiffstar/yiffchat, so it's been about 7 years along.
I most use it for the chat. The forums are ok, but the setup is very aesthetic in a way that reminds me of one of Gaias old layouts.
The chat has 100ish members at any given time, so you're bound to find someone to socialize with. I go there every day, as Yashendwirh.
And there's always livejournal. furry drama, furry drama 2, fursuits and others.