These are books, novels, texts, manuscripts, records, etc. that can be found online. Especially worth note are the religious and mythological texts, as they are a fountain of resource and inspiration material.
Title: Project Gutenberg
Notes: A vast collection of online books that have passed into public domain. Tons of classics to be inspired by, as well as many, many obscure works.
Title: Internet Sacred Text Archive
Notes: An enormous collection of online public domain texts relating to religion, mythology, occult, folklore, etc., ranging from ancient to more recent.
Title: The Schoyen Collection
Notes: A checklist and overview of 650 manuscripts spanning 5000 years.