Best source and most profitable to me is getting a job which pays you in bitcoin. Many on this forum pays bitcoin for those who can work Computer based freelance. Its better to work on your skills and develop them.
You should add an option "others", Coz i think best way to do a job and get paid in bitcoin, here is the ways
https://bitcointalk.org/index.php?topic=985550 But i don't use any of them till now, but for the past few months am demanding bitcoin as payment from my clients abroad, Since easier, cheaper & faster way to get paid.