The three stramps on the upper right are most probably definitives and were issued in 1998 showing what seems to be a space satellite. Perhaps these stamps pay tribute the launching of some space craft; I am not so familiar with this field of science, so that's all I can say about them.
The other stamp on the lower left is also a definitive issued in 1998, this time showing the logo of Πочта Рoccии, or Russian Post. A little history on them:
And now for the two beautiful commemoratives:
Russian Post is a founding member of the Universal Postal Union created in 1874. In 1902 Chief Postal Service was made part of the Internal Affairs Ministry and in 1917 under the Provisional Government it became part of Ministry of Post and Telegraph. During the Great Patriotic War Soviet postal service part of People's Commissariat of communications was delivering up to 70 million mails per month to the Soviet army front from the rear under extremely difficult and often very dangerous conditions.
In 1993 Russian Post became a part of Ministry of Communications and in 2002, its status changed from a government ministry to a Unitary enterprise in the framework of the restructuring the federal postal communication agencies. The company's headquarters are located in Moscow.
The one on the left, issued in 2007, pays homage to Vladimir Bekhterev, a Russian neurophysiologist and psychiatrist. Perhaps this stamp commemmorates his 80th death anniversary since he died in 1927. A little more on Bekhterev:
Bekhterev was the one who noted the role of the hippocampus in memory around 1900. Bekhterev founded the field of psycho reflexology, transferring Ivan Pavlov's work on dogs to humans. From his writings we can tell that he and Pavlov acted like enemies. He is most remembered for Bekhterev's disease.
In 1907 Bekhterev founded the PsychoNeurological Institute, later renamed the St. Petersburg State Medical Academy. He died in 1927, after an interview with Stalin, who presumably sought his expertise in dealing with depression. The facts of his death may never be known, but it has been speculated that the outspoken Bekhterev had diagnosed Stalin with paranoia, causing Stalin, who did not agree with the diagnosis, to have the doctor killed.
The cover on which the stamps are affixed is very nice as well. I wish I knew what that building was. Maybe the envelope has an explanation on the back like most of my other Russian covers do. I'll get back to this as soon as I can.
Finally, the stamps were franked on 28 Mar 2008 at Saint Petersburg, which is is often described as the most Western European-styled city of Russia and was the capital of the Russian Empire for more than 200 years (1713-1728, 1792-1918).