In addition to simply holding crypto, you can also lend it out as margin funding on sites like Bitfinex, Poloneix, or Magnr.com. The interest rates tend to be pretty low for crypto (e.g. 2.5% per year for Bitfinex on bitcoin), but it's another option!

There's always the risk of sites being hacked, so it's up to you whether you want to risk it or not. Is anyone providing margin funding? How have your experiences been?