Pastebin is often the hacker's tool of choice for posting exploits and information gleaned from them. But it does filter some content, and the site owner occasionally complies with law enforcement requests. So, Anonymous created its own version, called AnonPaste.
Anonymous describes the site as "a minimalist, open source online pastebin". The group says it won't filter out any content and goes on to claim that the "server has zero knowledge of data being stored. Your data is safe even in case of server breach or seizure." It says that data is encrypted/decrypted in the browser using AES-256, which it describes in some detail on the project page.
In other words, it's (claimed to be at least) a fully anonomised and more secure version of Pastebin for you to post your shenanigans, revelations and exploits without worrying about law enforcement or censorship. Caveat emptor, my masked friend. [AnonPaste via Ars Technica]