A collection of classic theoretical physics books, the Course of Theoretical Physics by Landau, Lifshitz, Pitaevskii and Berestetskii (English edition), is available online courtesy of the Internet archive.  It seems that the last two books in the 10 book series are not available, perhaps because their later publication dates meaning they have a longer copyright term. For a discussion on the copyright details of the books and the original source for my links see this Reddit thread. The Russian versions can apparently be found here although I have not verified this.