THE UPPSALA CORPUS OF RUSSIAN TEXTS
This is a one million words corpus created in the late eighties, when I was still working at the University of Uppsala. All information about the corpus and the frequency dictionary based on it can be found here.
Quite recently, in 2002, I was asked to write a short outline to be published in the HSK volume of Slavic languages. The title of this contribution is "Word frequency in Slavic, especially Russian". Here is an abstract.