A few online bibliographical resources for early medieval philology (with an Irish focus).
Bibliography of Irish Linguistics and Literature
https://bill.celt.dias.ie
Bibliographies for Theology
http://moses.creighton.edu/JRS/toc/bibliographies.html
Codecs: Online database and e-resources for Celtic Studies
http://www.vanhamel.nl/codecs/Home
CSANA: Celtic Studies Bibliography
http://celtic.cmrs.ucla.edu/csana/csanabib.html
Earlier Latin Manuscripts (founded on Lowe, CLA)
https://elmss.nuigalway.ie
International Medieval Bibliography
http://www.brepolis.net
Lexicon des Mittelalters
http://www.brepolis.net
Manuscripta Mediaevalia
http://www.manuscripta-mediaevalia.de/hs/kataloge-online.htm
Medieval Studies Bibliographies (Charles Wright)
https://bibliography.mip-archumanitiespress.org/
Mirabile
http://www.mirabileweb.it
Monastic Manuscript Project
http://www.earlymedievalmonasticism.org
NUIG Classics: Resources Online
http://www.nuigalway.ie/classics/resources-online/
Oxford Dictionary of National Biography
http://www.oxforddnb.com
Regesta Imperii (Mainz)
http://opac.regesta-imperii.de
Repertorium “Geschichtsquellen des deutschen Mittelalters”
http://www.geschichtsquellen.de
Scéla (Irish narratives)
http://mujweb.cz/enelen