Primary Texts
Are you looking for secondary liteature?
If so, look at Getting secondary literature
What do you want to do?
I want to identify an unknown text
AND I don't know what genre it is.
General purpose catalogue of incipits
In principio (Brepol(i)s, paywall 💵)
http://www.brepolis.net
AND it is a biblical gloss
Glossa ordinaria
A project for the electronic edition of the Glossa Ordinaria of the Bible - http://glossae.net/en/content/project-electronic-edition-glossa-ordinaria-bible
Old print: http://lollardsociety.org/?page_id=409
AND it is a sermon
Sermons
Schneyer: Repertorium der lateinischen Sermonesdes Mittelalters (1150- 1350) (book)
Schneyer: Repertorium der lateinischen Sermones des Mittelalters (1350-1500)(CD - hard to get)
Hopefully, an online version soon, see http://fordoc.ku-eichstaett.de/1885/
Should be finished in 2019
AND it consists of verses
Walther: Initia carminum ac versuum Medii Aevi Posterioris Latinorum
I want to search corpora of texts
See: Corpora of Latin Texts
I want to read texts easier
See Reading Latin text