What do other US citizens use to trade BTC with stop orders? I've been wanting setup an account to take advantage of short crashes like this but I'm not sure what exchanges are open to US citizens. And don't say BTCe, it must have transparency.
Be careful, stop orders only help if there is a reasonable amount of liquidity when you reach your stop price. If it's not there (and often isn't during a flash crash) you may get terrible execution.
If you are in the US the easiest way to get money into an actual exchange seems to be by buying BTC via coinbase (they support ACH transactions for US citezens) and then transferring it to an exchange such as Coinsetter, Bitfinex, or Bitstamp to trade. Coinsetter is based in the US and will rebate you your Coinbase transaction fees.