Greenpeace was founded in Canada in 1971 as a protest against American nuclear tests in Alaska. In addition to the more traditional environmental organization act of starting petitions, Greenpeace engage in non-violent direct action.
Greenpeace's tactics involve all kinds of "stunt" protests to attract attention to particular environmental causes, often spectacular "raids" of organisations of interest such as whaling vessels, nuclear plants, and the like. Such well-organised and often well-funded protests, with the use of one of Greenpeace's ships, fleet of inflatable boats, and the like, and the arrangement of extensive media coverage for the carefully-desgigned telegenic images that result), have attracted large amounts of attention to Greenpeace's environmental causes.
Their anti-nuclear protests in the South Pacific during the 1980's irritated the French government so much that several French intelligence officers were ordered to destroy the Greenpeace ship Rainbow Warrior, which was moored in Auckland(?), New Zealand in 1985, killing two (?) people. The subsequent revelation by an Australian TV show of the French government's actions greatly embarrassed that government and had the effect of increasing the effectiveness of Greenpeace's campaign.
Official website: http://www.greenpeace.org/