For free BTC, my mind comes only to BTC faucets and PTC sites... 
faucet and ptc only profitable if you have a lot of refferalsdon't waste your time, if you don't have any refferal
but if you already here, better to keep growing your activity so you can join signature campaign
best method to earn more bitcoins Buy a Full member account @ 0.07 btc and earn 0.14 btc amonth easly from 200 post per month
Roi is only 14 days 100 post
or buy a senior member account @ 0.25 btc and many btc per month