Śrī Matre Namaḥ,
Bhandarkar Oriental Research Institute Digital Library - Contains rare scanned books about the wisdom of the East but without subscription one can only preview 10 pages of any book and the annual plan for an individual is very nominal and affordable.
Forgotten Books - not scanned books but original prints of very old and rare books. And the website gives away one free book every day not just English but free books in five other languages. If you check every day you will get lucky getting old books which are not available anymore.
Śrī Gurubhyo Namaḥ
