Kanshu, Russians are absolutely into piracy:) So many 'Russian as a foreihn lnaguage' materials can also be found on the internet.
One place to look at is rutracker (our most poplar torrent tracker). Its collection is hardly comprehensive or representative, but they have section for русский как иностранный. May be you will find something interesting there, i don't know.
language.ws also used to have a huge collection of scanned language-related stuff, but it is not working lately.  May be also bookzz.
And of course, google books works for previewing things before you buy them.