BTC-E, Bitfinex, litecoinlocal.org, vircurex, crypto-trade, cryptsy, coinmtk, there are a few others. All I believe aren't located within the United States, so

BTC-E, Bitfinex, litecoinlocal.org, vircurex, crypto-trade, cryptsy, coinmtk, there are a few others. All I believe aren't located within the United States, so there is risk involved other than LTC being worth $0. I only suggest BTC-E based on it being one of the higher volume LTC exchanges.