More sheet music
Facsimiles and critical modern editions of viol music: A guide through the web
J. S. Bach, C. P. E. Bach, Altbachisches Archiv etc.
Gallica is the digital library of the Bibliothèque nationale de France and its partners.
The Partiturbuch Ludwig includes several compositions with viola da gamba obbligata.
The International Music Score Library Project (Petrucci Music Library) provide music scores free of charge. Many facsimiles are included.
The collection of Padre Giambattista Martini and more
e.g. Marais, book II
Important collection of 17th century music, Buxtehude, Bertali, Jenkins, Tunder etc.
Music for viols and more. Mostly polyphonic music in practical editions, with separated parts.
In ChoralWiki, the Choral Public Domain Library, you will find free choral/vocal scores, texts, translations, and other information.
The International Music Score Library Project (Petrucci Music Library) provide music scores free of charge. Many facsimiles are included.
A collection of modern editions dedicated to Renaissance and Baroque music scores, with an accent on music for (or suitable to) viola da gamba or viola da gamba consort.