Wikileaks is a website that publishes anonymous submissions and leaks of sensitive governmental, corporate, or religious documents, while attempting to preserve the anonymity and untraceability of its contributors.

And yes, it's reliable. Many companies, governments and religious groups (especially $cientology) try to get documents removed from the site because they're afraid of what the documents may reveal to the public. If the documents were not the real thing, they wouldn't have reason to be worried about it.