You can use bitfinex.com and gain an interest payd every day. The site is one of the most trusted exchanges. You can exchange, trade on margins (short bitcoins) and lend your fiat or bitcoins.
Use the code 5l4wLVc4LW when making a new account for a 10% discount on all fees.
you should also mention the code = an affiliate code which means you get some profit aswell with that code of the trades .
be fair and honest.
other thand that.. the interests are crazy and high but real! due to bigger demand then offer apparently ppl seem to pay 0.2 -> 0.6% a day
good luiquidity, shorting and longing on margin ... .