One for the toolbox: Forgotten Books online
A great resource I've been digging lately is ForgottenBooks.org, where you can read thousands of books online for free or purchase in paperback at wholesale prices. I ordered collected writings of Clarence Darrow and a few other lovely old chestnuts. I've also taken advantage of the nifty Google feature to search inside.
From the website:
We specialize in historical writings, this includes works such as: classical fiction, philosophy, science, religion, folklore, mythology and sacred texts, in addition to secret and esoteric subjects, such as: occult, freemasonry, alchemy, hermetic and ancient knowledge. Fiction and non-fiction books.
It is our mission to find hidden knowledge and preserve lost knowledge, from antiquity to the present day, and make this information freely available to the world.
Check it out.