The Public Domain Review is an “online journal and not-for-profit project dedicated to the exploration of curious and compelling works from the history of art, literature, and ideas” who’s claimed aim is to “promote and celebrate the public domain in all its abundance and diversity, and help their readers explore its rich terrain – like a small exhibition gallery at the entrance to an immense network of archives and storage rooms that lie beyond.”
Lots of good stuff there to get lost in and a good research tool as well.