I had a look through this site, so I’m not sure it was not already posted, but here are two important links to find many Russian books. The largest repository I think is http://www.eknigu.com, they also have Russian versions, and the second is only for lucky people who can understand Cyrillic 🙂 http://www.mccme.ru/free-books/ … it contains also many un-translated booklets, including some little treasure by Arnold (use Google to translate at least the site content). Final suggestion: similar to http://www.arxive.org, may be not so large!,, also exists http://gallica.bnf.fr/. Ciao