There's a ton of primary source material out there on the web -- sometimes a simple Google search will unearth links to diaries of soldiers or newspaper articles from the Civil War. Most of this stuff is out of copyright, so it's available to be used.
Civil War Soldiers: Selected Diaries & Letters Online
General:
Union
Confederate
From the Homefront: Correspondents and Diarists
North
South
Miscellaneous:
House Divided Project
Gilder Lehrman Institute
Dred Scott Case