JoinMarket (warning: experimental, as far as I know) may be used to gain a tiny interest for providing coins for CoinJoins:
https://bitcointalk.org/index.php?topic=919116.msg10096563https://www.reddit.com/r/joinmarketTo quote:
Elevator Pitch for Investors
Firstly I'd like to clarify what I mean by investing. I don't want you to give your bitcoins to me. I dont want you to give your bitcoins to anybody. The private keys would be safely held on your own computer, known only by you and your wallet.
Features:
1. Earn an income from your investment bitcoins.
2. Very low risk. Your coins have to be on an online computer, but the software would only sign transactions that are valid and pay you the correct amount.
3. No commitment, withdraw your bitcoins at any time.
4. Improves the privacy of the bitcoin transactions, which makes bitcoin as a currency more useful and thus increases its value.
5. Improves the fungibility of bitcoin, since the distinction between 'clean' and 'dirty' bitcoins will be meaningless. Eliminates this particular systemic risk to bitcoin.
Downside:
1. Your return is likely to be quite low. Low risk = low reward.
2. You don't get paid unless people who desire privacy actually use this. If you're an investor you have an incentive to tell people about JoinMarket.
Some Dice sites allow to deposit coins for the house, where gains (and losses) are shared.
But in general, I share the sentiment: better check these things twice, before giving away the control over your bitcoins.