National Security Archive

The National Security Archive is a 501(c)(3) non-governmental, non-profit research and archival institution located on the seventh floor of the Gelman Library building at the George Washington University in Washington, D.C.. Founded in 1985 by Scott Armstrong, it archives and publishes declassified U.S. government files concerning selected topics of US foreign policy. The Archive collects and analyzes the documents of many various government institutions obtained via the Freedom of Information Act. The Archive then selects documents to be published in the form of manuscripts and microfiche as well as made available through their website, which receives a half-million downloads daily. According to a Washington Post feature story, the Archive files roughly 2,000 FOIA requests annually, collecting about 75,000 documents. The Archive appealed 549 FOIA decisions in 2006, and has filed more than 40 lawsuits to obtain compliance with its requests

More information on the Wikipedia page

The website is.