Last year, while taking a Russian course here in Saint Petersburg I stayed with a russian family (well, I should say "there", I wish I were "here" again :).
They have asked me to help them to find a new tenant. So, if you are planning to go to this incredible city to study this incredibly difficult (but beautiful) language, please send me a private message and I will provide you the email address of my russian family.
Ah! This family is really really nice. You know? In the two weeks I stayed with them, I had to prepare sangria 3 times! And many days I had to have 2 dinners! (Natalia cooks very well, I recommend you the half board at least).
The apartment is located in a very nice area, not far from a park, and more or less to the same distance from Gorkovskaya and Sportivnaya metro stations.