LibGuide Community http://libguides.com/community.php?m=i&ref=libguides.com (or browser search).
The LibGuide Community is a collection of published LibGuides from school and library communities. Guides are public and much is available for use.
A very good source for Primary sources. More for teacher directed than student exploration. Potential use for Social Studies DBQs (Document Based Questioning).
What is a LibGuide? http://sunyjcc.libguides.com/WhatIs
Creating Libguides from The Best Practices... http://bestof.libguides.com/content.php?pid=414724&sid=3389879
Social Studies DBQ example: Did America drop the Atomic bomb to end the war with Japan or to intimidate the Soviet Union?
Search LibGuide Community for World War II primary sources select > WWII Primary Sources - University of Washington select > Atomic Bomb and the End of World War II.