the volume seems very thin on the exchanges (BTER for example). i'm interested in buying a few BTC worth, but not sure how i do so with such low volume. yes XMR is trading at .004 as of this writing, but there's only about 1BTC of buy orders between .004 and .003.
https://poloniex.com/exchange/btc_xmrVolume ranges from 150 btc per day to 1000 btc per day for Monero alone.
Unless you want to buy 50 btc worth I'd suggest poloniex as the most suitable market. Over a 24 hour period you'll easily get <50 bitcoin worth at market rates without moving the market too much. However for amounts larger than 50 btc you might want to check out irc freenode #monero-otc for potential sellers/buyers.