The best site for LTC/BTC trade is
Btc-e.com. I'm surprised to see that no-one mention it yet. I don't really get why people suggest you low volume, untrusted sites. Btc-e is your best bet.
Agreed BTC-e is a great exchange and is the best for LTC volume. Shapeshift.io for small volume works amazingly well. Also people will say that BTCe is some how shady - all exchanges are shady, but I actually trust BTCe over most.