Click here to access the UN's archive of The League of Nations (which is another online guide like this one).
The Aftermath of WWI
Lead Up to War - WWII
Click here to read an excerpt (PDF) from this book[from Lick-Wilmerding High School]
Click here for a long list of links to primary source documents relating to the interwar years.
Search for digital objects between 1917-1937 in the World Digital Library