While collecting space related covers I was always driven by space flights and all around, mostly ignoring the basis of the space program – research, development, production and training facilities. Speaking generally this is a topic by itself as there is a huge number of various institutions related to space exploration – starting from the rocket design bureaus and to the production plants. I will try to focus on the most obvious like RKK Energia but possibly there will be a less known stuff. I also include here observatories as I do not have a dedicated page for astronomy.
I have no intention to create a reference list of the facilities, just presenting what I have. In case you want to get more information on this or that organization or place - GOOGLE.com is at your service.