If you're looking for digital resources for musicology - say, digitized Beethoven scores - then this new website looks really useful. Do take a look to see if it has anything relevant to your area of study or teaching!
This website provides links to substantial open-access projects of use to musicians and musicologists. With a burgeoning number of digital resources available, remembering titles of sites and pathways to them can be difficult. Digital Resources in Musicology (DRM) is organized topically and provides a rapid search tool for specialties within heterogeneous collections. Neither the links or their descriptions are exhaustive.
Older projects predating the development of the internet are listed at ADAM: Archive of Digital Applications in Musicology. Curated digital and hybrid editions are itemized at EVE: Electronic and Virtual Editions. Harvard's Online Resources for Music Scholars offer a somewhat different, largely complementary mix of projects.