The Institut für Neutestamentliche Textforschung:
New Testament Virtual Manuscripts Room: http://ntvmr.uni-muenster.de/
The online Kurzgefasste Liste: of manuscripts http://ntvmr.uni-muenster.de/liste/ (includes bibliographic references, although some of them -- like the one to this site -- are very out-of-date)
Brown University Textual Criticism Materials
Quartz Hill School of Theology
CEU Coursein Textual Criticism
TC: A Journal of Biblical Textual Criticism
TC or TC
The University of Michigan Papyrus Collection
Index of Biblical Quotations in Early Christian Literature
Electronic Resources for the Textual Tradition of the Epistles Of PaulMaster page with links to collations of manuscripts of Galatians and Ephesians plus other projects.
Scrivener's Plain Introduction
Hutton's Atlas of Textual Criticism
Hammond's Textual Criticism Applied to the New Testament
(Note that these books are mostly pre-Gregory.)
Greek Texts (and Interlinear Bibles) page
Note: Much of what this points to is Textus Receptus- derived, and has no value. In fact, it's quite irritating. But it also points to the Scrivener/Miller Plain Introduction, which is still the single best source of information about the manuscripts known at the time it was published.
The FarAboveAll Translations page
Bible resources, including English translation of the Robinson & Pierpont text, with Greek text and notes, and various Textus Receptus editions. Not much direct textual criticism here, and I don't endorse what there is, but useful for understanding the Majority Text (as opposed to the Textus Receptus).
Thanks to Donna Waters for updates on some of these sites; she is a volunteer for Addiction Resource (https://addictionresource.com/alcohol/) and VapingDaily (https://vapingdaily.com/), sites to deal with addiction problems. (Please note that I cannot vouch for the work of these sites.)