The Fundamental Digital Library of Russian Literature and Folklore is an incredibly rich and valuable digital resource, particularly as it hosts many academic redactions of classic works by Russian writers. A good substitute when you don't have the PSS on hand.
The Russian National Library maintains this excellent resource, listing sites of access for digitized journals and newspapers across the internet. Organized chronologically, thematically, geographically, and linguistically, this is an essential checkpoint if you're seeking a specific title.
An evolving digital library administered by the Russian National Library, including digitized rare books, periodicals, and images.
The digital library of the Nekrasov Library.
The digital library of the State Public Historical Library. Includes books, journals, newspapers, images, and maps.
A variety of digitized resources, including digitized periodicals and books.
A "noncommercial digital library" featuring books as well as audio clips, images, articles, etc.
Digital collections documenting chiefly underground activity during the Soviet period, including many films.
Digital collections created through a British Library-funded grant program that sends researchers to "endangered" research collections for preservation work. Many collections from Russia and Eastern Europe are included.