Miller Center

Here is another site with links to yet other sites that contain declassified files from the Cold War, including those from the Soviet archives after the Soviet Union collapsed: http://millercenter.org/academic/dgs/primaryresources/cold_war."

Digital National Security Archive
This archive, available from ProQuest, holds "the most comprehensive collection available of significant primary documents central to U.S. foreign and military policy since 1945. Over 58,000 of the most important, declassified documents—totaling more than 450,000 pages."
Avalon Project - Cold War Document Collection
This project at Yale Law School contains a wide variety of document collections. This Cold War collection offers users groups of official US government documents through the 1960s. Also, check out the Cold War Diplomacy - Defense Treaties of the U.S., 1941-1954.
Documents Relating to the Cold War
Begin your document search here. This site, maintained by the International Relations Program at Mount Holyoke College, contains a plethora of Cold War diplomatic documents.
HistoryWiz: The Cold War
This collection ranges from primary resources online to links to various online exhibits and museums. Categories include: General Resources, Cuban Missile Crisis, Arms & Space Race, Vietnam War, Korean War, and Berlin Wall.
The Cold War Files
This website, maintained by xx, contains a wealth of resources, especially primary resources, from political leaders throughout the Cold War era. The most useful tools to researchers will probably be the Entire Document Collection and the Resources section, which has links to further reading.