I wanted to dump my SONM but Hitbtc paused deposits and withdraws. The best price was there, I tried Etherdelta next but it's very slow in deposits. There's no good buy order too. I think we have to wait a little more to sell.
Why don't you try liqui exchange platform? They also have SONM in their market. I think the best volume is on liqui exchange at the moment. The rest is very low trade volume like etherdelta and hitbtc.