The most useful 21 links

1. Digitized manuscript catalogs (Brigitte Pfeil)

https://www.ub.uni-kassel.de/handschriftenkatalogeonline.html
https://www.uni-kassel.de/ub/historisches-erbe/sondersammlungen/handschriftenkataloge.html

Please mail Ms. Pfeil additions: pfeil at bibliothek.uni-kassel.de

2. Online catalogues of medieval manuscripts (Albrecht Diem)

https://www.earlymedievalmonasticism.org/Catalogues-of-Latin-Manuscripts.html

3. Handschriftencensus manuscript catalogs

https://www.handschriftencensus.de/forschungsliteratur/kataloge

4. Medieval Manuscript Catalogs & Inventories (Robert D. Peckham)

https://www.utm.edu/staff/bobp/vlibrary/mscatalogs.shtml

5. Kristeller Online: Latin manuscript books before 1600

https://www.mgh-bibliothek.de/kristeller/

Please note that there is a printed addendum published in 2006.

6. Peraldus.ch: A collection of bibliographical references to medieval
manuscripts

https://www.peraldus.ch/

7. Looking for a manuscript in the publication Scriptorium and in the Bulletin codicologique

https://www.scriptorium.be/search_manuscript.php?lang=en

8. Hill Museum & Manuscript Library

https://www.hmml.org/research2010/research10.htm

9. Schoenberg Database of Manuscripts

https://dla.library.upenn.edu/dla/schoenberg/

AUSTRIA

10. manuscripta.at - Mittelalterliche Handschriften in
österreichischen Bibliotheken

https://manuscripta.at

BELGIUM/ THE NETHERLANDS

11. Bibliotheca Neerlandica Manuscripta

https://www.library.leiden.edu/special-collections/manuscripts/subcollections-whs-bnm.html

12. Medieval manuscripts in Dutch collections

https://www.mmdc.nl/

13. Online guide to mediaeval manuscripts in Wallonia - Brussels

https://www.cicweb.be/en/recherche.php

EAST EUROPE

14. Manuscriptorium

https://www.manuscriptorium.com/

Mostly Czech Republic

FRANCE

15. Bibliothèque virtuelle des manuscrits médiévaux

https://bvmm.irht.cnrs.fr/

16. Enluminures, Liber Floridus, Mandragore

https://www.manuscritsenlumines.fr/

17. Initiale - Catalogue de manuscrits enluminés

https://initiale.irht.cnrs.fr/

GERMANY

18. Manuscripta Mediaevalia

https://www.manuscripta-mediaevalia.de/

Please note: There are (i) descriptions and digitized catalogs in the
database, (ii) an old presentation of older digitized catalogs where
you can link directly to pages at

https://www.manuscripta-mediaevalia.de/hs/kataloge-online.htm

(iii) PDF-descriptions in the section "Projekte" which cannot be
searched (respective incompletely via Google site:search)

ITALY

19. MANUS - Censimento dei manoscritti delle biblioteche italiane

https://manus.iccu.sbn.it/

SWITZERLAND

20. Verbundkatalog HAN

https://www.ub.unibas.ch/?id=1469

Mostly modern materials but also medieval mss. from Basel, Luzern, St. Gallen (Vadiana), and Solothurn (to mention only the most important libraries with medieval manuscripts)

USA

21. Digital Scriptorium

https://bancroft.berkeley.edu/digitalscriptorium/

UPDATES

May, 2014

I should have mentioned

FRANCE

Calames
https://www.calames.abes.fr

July, 2014

Bibliografia dei manoscritti citati in rivista
https://tlion.sns.it/mssb/

December, 2014

MIRABILE
https://www.mirabileweb.it/

USA

Directory of Collections in the United States and Canada with Pre-1600 Manuscript Holdings
https://bibsocamer.org/wp-content/uploads/Conway_Davis_2014.pdf