Fordham University provides a list of links to online primary sources from the modern era. Also, this website has a section on: Soviet Russia.
This is a multi-media archive of primary materials designed to introduce students and the general public to the richness and contradictions of Soviet history.
An online academic database used by universities worldwide that is a superb resource for History students. To view full articles, you will require membership.
This searches internet sites for academic articles and books. It often only provides one or two pages, but it is often enough to find quotes and bibliographical details.