Biblindex – Index of biblical quotations and allusions in Early Christian Literature; requires account information (free)

Blue Letter Bible – Searchable Bible database with links to Strong’s Concordance as well as Greek and Hebrew texts, standard versions/translations, related commentaries, hymns and maps.

Gutenberg Bible – Online access to the British Library’s two copies of Johann Gutenberg’s Bible (circa 1450).

Resource Pages for Biblical Studies – Intended as a resource for serious, scholarly studies of the early Christian writings and their social world.