If you are looking for leverage trading check out BitMex or Bitfinex. Other famous trading platforms are Bitstamp, Quoine and Poloniex.
You can read more about these trading companies and other Bitcoin trading tools at
www.cryptocointrade.comin bitmex support lending system same in bitfinex service or not
and margin trading in bitmex same use bitfinex system or not, and how much return lending in bitmex(swap system)