* The Dwight D. Eisenhower Library
This site contains a comprehensive collection of primary sources including press releases, notes, letters, records of telephone calls, and situation reports.  The documents are authentic, scanned online, and viewable in their original format.  The Eisenhower Library is administered by the National Archives and Records Administration and is therefore, a reputable source for the papers and other relevant historical documents pertaining to our 34th President.

* The National Archives
An extensive collection of American historical documents and pictures.  Extremely useful in a search for contemporary history.

* American Memory
Using the search terms “Earl Warren,” I encountered some personal notes from Justices Douglas, Burton, and Blackman to Warren concerning the Brown verdict.  Since I did not have access to the Earl Warren Papers, this online version (where the actual letter is viewable) reveals the gratitude the men felt towards Warren for his leadership role.  This site is a fabulous tool for researchers in American history, especially more contemporary history, based not only on its size but also by its backing from the Library of Congress.  I was able to access some images as well.  Its versatility was quite useful to me in my research.