Pre WW I Russia was even bigger than it is today. Germans were scattered in many different regions.
There are actually 3 different English language societies that serve Germans from Russia, each having unique focus and characteristics. Since this forum is generically for all Germans from Russia, I thought I would add them here. There are other German ones as well.
The one mentioned previously GRHS, with headquarters in Bismarck, ND is focused on the Black Sea (including Crimea) and Bessarabia regions. http://www.ahsgr.org
is based in Lincoln, NB and features the Germans from the Volga River settlement region.
Both of the above have resources for other areas but to a lesser extent.
The third, http://www.sggee.org
has a mailing address in Calgary, AB but doesn't have a corporate structure or offices like the others do. It is a registered Society but is Internet based with officers and members from around the world. It is highly focused on Germans from Volhynia (northwestern Ukraine) and Russian Poland with support for Kiev and Podolia regions. It has no resources for the regions covered by the other two societies.