We have found this site, http://www.bookfi.org/ which claims to contain close to a million scanned Russian books, especially useful for Russian etexts. It also claims itself to be the largest electronic library of the Russian net. It is not possible for us to verify these claims, but preliminary searches have shown that one can find many digital versions of works on the site that are not available anywhere else. An example of such a work is Sovetskaia voennaia entsiklopediia. (One would assume that it would be impossible to find this work online for free due to copyright restrictions).
The site has a search engine, which allows for keyword or exact phrase searches. A quick browse of the results of a search using bibliografiia, shows that the site would be of great interest to serious researchers.
Below is an example of a sample hit in the database.