Other writing sites?

Let me start by saying that I feel absolutely at home here - I can agree/disagree with people - and even bicker - almost as much as at home! And I think the standard on here is excellent.
I just wondered what the general consensus was about joining other writing sites at the same time.
I've seen some pieces of writing on UKA that I recognise from here - sometimes by the same nickname, sometimes not. I wondered whether the ones who post their pieces on multiple writing sites gain much more exposure that way, as it tends to be the same people visiting all the sites. I agree that the more exposure you can give yourself the better, but if you have some experiences to share, I'd be very interested.
Would it be better to join these writing sites but put different pieces on each of them, so your exposure is extended that way?
Or can any of you recommend some particularly good writing sites other than this one? Or some stinkers?