Your research may lead you to investigate both primary and secondary resources.

Primary resources are the basic evidence for any good research project, and can come in many formats: documents from archives, interviews or eyewitness accounts, newspaper articles, video footage, etc.  For example, if you were examining the political relationship between the Allied powers during WWII, you might look at primary sources such as diary entries, correspondence and/or interviews given by the key political figures of that time period.

   American Foreign Policy: The Twentieth Century in
   Documents

   This book is a compilation of many primary
   resources, including speeches and other
   correspondence.

Secondary resources are also valuable to use as sources for your paper, and are works that interpret, analyze, and often synthesize primary source materials to give a broader understanding of a certain topic.  These may come in the form of scholarly books or journals.  They often cite primary source materials, but are a step removed from those events.

   FDR & Stalin: A Not So Grand Alliance, 1943-1945

   This book is an example of a secondary resource: a
   scholar presenting the results of research he has
   done regarding the alliance between FDR and Stalin.

The American Historical Association (AHA) is a nonprofit membership organization for the promotion of historical studies, the collection and preservation of historical documents and artifacts, and the dissemination of historical research.

Phi Alpha Theta is one of several organizations that presents scholarly information in the field of history through conferences and publications.  This link may provide you with information related to current inquiries in the field and new initiatives. Think "hot topics" in history.