Biblioteca Nacional Digital :: BrasilRanking the World's Best Digital LibrariesGeneral Digital Libraries The digital libraries on this list hold the most comprehensive collection of library materials available for free online. Some of them are so old that they actually predate the web. Universal Digital Library - The million book collection. Project Gutenberg - More than 20,000 ebooks, audio books, CDs and DVDs. Bartleby - Huge collection of reference, verse, fiction and nonfiction books. ibiblio - Library and digital archive offering ebooks, academic papers, software, music, and streaming radio. Many of the nation's top colleges and universities host their own digital library collections. Online Books - More than 30,000 books from the University of Pennsylvania. International Digital Libraries Digital libraries are a worldwide thing. International Children's Digital Library - Fabulous collection of children's books (historic and modern.) Honorable Mentions The following digital libraries also offer excellent materials.