The Marxist Internet Archive (MIA) has an archive of Marxist publications, including the most famous contributions to the study of the New Testament and Christian origins. These are:
Frederick Engels, The Book of Revelation (1883)
Frederick Engels, Bruno Bauer and Early Christianity (1882)
Frederick Engels, On the History of Early Christianity (1894)
The Online Critical Pseudepigrapha (OCP) provides open-access, online critical editions of various Jewish and Christian pseudepigrapha. OCP is a publication of the Society of Biblical Literature (SBL).
To date, the site provides critical editions (with critical apparatuses, which show variants in the various manuscripts) for some works, and provides other texts without critical apparatuses. The project is ongoing, so “readers should consult the ‘text status’ information on the introductory page for each document to determine whether a better or more complete text exists elsewhere.”
The current available texts are:
Texts with critical apparatus
2 (Syriac Apocalypse of) Baruch
The Testament of Job
1 Enoch (In progress)
Testament of Adam (In progress)
Texts without critical apparatus
Testament of Abraham
The Life of Adam and Eve
Visions of Amram
The Letter of Aristeas
Aristeas the Exegete
Aristobulus
Artapanus
3 (Greek Apocalypse of) Baruch
4 Baruch (Paraleipomena Ieremiou)
Cleodemus Malchus
Eldad and Modad
Eupolemus
The Apocryphon of Ezekiel
Ezekiel the Tragedian
Vision of Ezra
The History of the Rechabites
Jubilees
The Lives of the Prophets
Assumption of Moses (Testament of Moses)
3 Maccabees
4 Maccabees
Philo the Epic Poet
Pseudo-Eupolemus
Testament of Solomon
Theodotus
Biblical Studies Online 