Pros: social atmosphere, travel, free events, fulfilling work, free socials, music festivals, etc
Cons: makes it hard to maintain a personal life separate from work
My experience with Greenpeace was, overall, a positive one, with a few exceptions.
During my time with Greenpeace, I grew, learned, experienced, and achieved quite a bit. I was in charge of coordinating events and volunteers on the local level; fundraising, training, and opening offices on the national level. I participated in events from California to North Carolina, Montana to Texas. I have been pictured in the newspaper dressed as an iPhone at Apple's headquarters in Cupertino, and featured on the news in Portland, Maine as part of an anti-whaling protest.
The job culture is simply sublime. I met my closest friends through my work with Greenpeace, and continue to be part of the culture to this day. They have weekly socials, engage in team sports, and encourage volunteerism during non-working hours.
Although the culture great, it also contributes to the poor work/life balance I experienced with Greenpeace. I had lived in Colorado for three years while working for Greenpeace, and had not made any social life for myself outside of work in that time. With all the traveling and relationships with co-workers, it creates an almost cult-like environment with little interaction with the outside world (we would actually joke about bringing new people to socials and introducing them to our office culture as 'drinking the kool-aid').
I wouldn't trade my time with Greenpeace for the world, but, in retrospect, I would like to have made more of an effort to have a better separation between my professional and personal life.