I am thinking you are still at amateur level in bitcoin activities. Ok honestly if you are asking then i would like to tell that, till today i didn't find any great sites which give high interest on bitcoins or any kind of high returns on investment. But i would recommend you to go for trading and investment by your self study which is the best way to earn good money . Learn the technical analysis subject in trading and practise them well and then go for trading in your live account, which will give your money back in easiest possible way.