I applied online. The process took 4 days. I interviewed at Greenpeace (New York, NY) in May 2015
Interview
Very lax. Told me they wanted me almost before the interview ended. They had about 9 people in their office and had them wait their turns to get interviewed. First the leader dude briefed us all about the organization.
I went through one interview via the manager in the main office. It was a few questions and overall very easy. I was first approached by another canvasser on the street and pulled in for an interview.
One interview and then a three day period to get 3 new members, team was helpful in supporting you. Some of it is luck of the draw though, I moved to Boston before securing this and it could have very easily not worked out