Digital Yiddish Library
https://www.yiddishbookcenter.org/collections/digital-yiddish-library
The Digital Yiddish Library includes works of fiction, memoirs, poetry, plays, short stories, science manuals, cookbooks, primers, and more, all from major authors writing in Yiddish. Since 2009, they've made over made more than 11,000 titles available online.
The Isaac Bashevis Singer Archives
https://www.bashevissinger.com/archives
The Isaac Bashevis Singer Archives include notes, letters, drafts, interviews, and much more from Singer's and his close friends' personal collections of his work.