Hello OP
How much is it possible to win ?
huh? I guess it is OP has made it very clear....
1.
http://freebitcoinz.com/This site pays you 3000 satoshis per day for filling out 3 captchas.
2.
http://freebitco.in/The payout every hour is based on the value you roll. If you are lucky, you can win up to 0.22 bitcoins just by simply filling out the captcha and clicking roll.
3.
https://www.999dice.com/their faucet pays out 999 satoshis every 10 minutes for you to try your luck.