...
At first it might need someone to make a market to get the trades going. I would be more than happy to do that, as that is kind of my day job. Anybody can place orders in the orderbook, just need to select the NXT/USD or NXT/BTC pair.
...
I have many XRP

And some btc and usd @Stamp..
I purchased about 1.3k of NXT on the Peercover BTC/NXT orderbook a few hours ago, but it's kinda sparse:

I look forward to seeing more people trading there soon.
Check NXT/XRP. You can convert XRP to BTC.