coinexchange.io I suppose is the main place to buy/sell beans right now. It is also listed on smaller exchanges (not that coinexchange isn't already small) -- btcpop and maybe novaexchange, but they won't have much volume.
Actually, BTCPop.co has pretty good volume. I would say they are at least comparable to Coinexchange.io.
Yeah, btcpop is okay for volume too, relatively speaking. Of course when we are talking about daily volume for a coin in the $500-$1000 range, I wouldn't say any current bitbean exchange has much liquidity.