USA friendly margin trading exchanges:
We've tried them all. These 3 brokerages are the best for trading leveraged cryptocoins. USA traders are welcome at each of the below.
The simplest interface to learn. 1Broker trades most markets, but is limited to bitcoin for cryptocurrencies. You can select any amount of leverage up to 10:1 for bitcoin trading. It has one of the cheapest bitcoin financing rates at 0.3462%/day, making it a good candidate for longer term investing of leveraged BTC. I could almost use them exclusively if they offered more crypto pairs. The minimum trade size is .01 BTC, and withdraws are .0015. Lastly, they have a great android app, with iOS on the way too.
WhaleClub is newer, but growing. It has the best charting there is. The whole site is fast, and it's extremely easy to make trades once you know how. WhaleClub has the highest BTC/USD I have seen, with 20x leverage (5% up earns you 100% profit)! Click the white + in upper right, it will open the buy/sell order box. You can select the amount of leverage you want via drop-down, and either sell short, or buy long! Your positions are all displayed below the chart, which you can resize up or down, and scroll though them too. WhaleClub offers a few crypto pairs including, btc, eth, xmr, ltc, and dash. Of course there are the usual items like stocks, FX, bonds, and commodities too. Bitcoin financing is 2% daily, which is normal, albeit a lot. Other cryptos, such as LTC with 0.4% daily financing is a lot easier to swallow.
SimpleFX is more advanced, and offers some extremely high margin. You can buy BTC/USD for 1:10 or LTC/USD up to 1:16.67! That means for every $1 you put up, they put up $16.67. With such high leverage, a 6% move one way or another will double your money, or put you to 0! You don't need to opt for such high leverage, it takes some exploring to figure out how to change your margin amount on each account though. You can have up to 10 trading accounts on your login, which you may switch between. Each is segregated from another, so if you lose it all on one, it wont affect your others. You can also set different leverages for each trading account. The best part about SimpleFX is that on some pairs you can do very small trades, like .002 will get you a small position. It's very easy to scale, but very easy to get in over your head! Be careful with heavy leverage.