The Open Access DTL
The OADTL is free for all persons everywhere and requires no membership or registration. It does not collect any personal information about patrons. The library contains over 250,000 ebooks, about half from the last 25 years. The OADTL has hundreds of thousands of regular users in nearly 200 countries.

Google books
In addition to searching inside books, Google Books, along with, makes freely available texts that are in the public domain. They aim to make every book ever published full-text searchable within ten years.

Google Scholar 
A heavily used search tool that indexes the majority of periodicals that are available online. Google Scholar also indexes the articles themselves, if they are available online, although a user needs to have access through a library or personal subscription to read or download them. Google Scholar simultaneously searches Google Books.

The Theological Commons
The Theological Commons is a digital library of 78,924 books and periodicals on theology and religion, including 29,322 volumes from the Princeton Theological Seminary Library.

Duke University Open Library
Duke's open access resources for the study of religion and theology.
DOAB is a community-driven discovery service that indexes and provides access to scholarly, peer-reviewed open access books and helps users to find trusted open access book publishers. All DOAB services are free of charge and all data is freely available.

Digital Public Library
Discover 47,210,791 images, texts, videos, and sounds from across the United States

Pictorial Bible Commentary is a large, unique, multilingual web site which presents an overview of the Christian Bible. The English section has over 800 pages and over 500 images.
Download free books and texts. The Internet Archive Text Archive contains a wide range of fiction, popular books, children's books, historical texts and academic books.

Christian Classics Ethereal Library
The Christian Classics Ethereal Library is a digital library of hundreds of classic Christian books selected for edification and education. The online server reaches several million different users each year.

Bible Study Tools
An online collection of Bible versions and translations, commentaries, concordances, dictionaries, and works by important Christian theologians.
Makes high quality theological material freely available throughout the world, thus providing Bible teachers and pastors with the resources they need to spread the Gospel in their countries.

Early Church Texts 
Gives access to complete Greek and Latin texts which are in the public domain, and to translations (where found available) from the first five centuries. It features carefully-indexed links to authors and their works.

The NTS Library
The Online Theological Library provides both students and scholars with vast resources of reference materials. It was created with the intention of providing a means by which you can complete research and study from one location. In the process it was decided to allow free access to all who desire to increase their knowledge and understanding of theological issues or for just personal study.

Project Gutenberg
Project Gutenberg offers over 57,000 free eBooks. Choose among free epub books, free kindle books, download them or read them online. You will find the world's great literature here, with focus on older works for which copyright has expired. Thousands of volunteers digitized and diligently proofread the eBooks, for enjoyment and education.