As many said there - the one of the fastest ways to earn is gambling... I don't appreciate it so much, because it's risky. Bitcoin is hard to earn and easy to lost. As normal money in casino. I checked this site from post above. They got affiliate program and you can earn some btc. onehash.com
But I'm not sure if I would try betting. Maybe if I will got more bitcoins from their program. But you know it's fun to earn money on betting site without betting xD