Please check out this post on Rea Andrew Redd's Civil War Librarian blog.
A Virginia collector has donated almost 700 rare Civil War era photos to the Library of Congress. The majority are ambrotypes (on glass) or tintypes (on metal) and are of common soldiers. Some are identified while others names have been lost to history. The LOC is planning an exhibition of the photos in April 2011 to coincide with the 150th anniversary of the start of the war. Many have already been digitized and are available online.
Click here for the LOC announcement.