Have You ever heard about a wallet-cum-faucet, which pays you 4.08% interest on your deposit annually. It is freebitcoin.
you can also earn free bitcoin without deposit. for that you have to roll in free btc section of the website(you can roll one time per hour). there you can win upto 200$ worth btc (0.02306882 btc) every hour.
The good thing is you start earning interest right from the first day! (0.0109589% per day and rounded down to the nearest satoshi).