The Internet Archive is one of the world's largest repositories of digital materials: "The Internet Archive is a 501(c)(3) non-profit that was founded to build an Internet library. Its purposes include offering permanent access for researchers, historians, scholars, people with disabilities, and the general public to historical collections that exist in digital format."
Its holdings include the Digital Yiddish Library of the Yiddish Book Center, the largest source of Yiddish materials in the Internet Archive, but there are several other Yiddish materials as well. Find them by searching with the keyword 'yiddish'. you can narrow down the search results by collection (or other criteria).