arXiv is a free distribution service and an open archive for scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics.
The Internet Archive Wayback Machine is a service that allows people to visit archived versions of websites. Visitors to the Wayback Machine can type in a URL, select a date range, and then begin surfing on an archived version of the web.
Open Library is an Internet Archive open project which aims to create a virtual library catalog with a Web page for every published book. Currently, Open Library has more 20 million book pages, which may be searched by author, title, or edition. Approximately 1 million of these books are available as free e-books in the public domain. When possible, a book’s Web page has links to assist with borrowing or purchasing a copy.