Russian
Russian, written in the Cyrillic alphabet, is the principal language of the Russian Federation, and was previously the official language of the Soviet Union. As a result, it is an important language in all of the former Soviet Republics in the Baltic (Lithuania, Latvia, Estonia), the trans-Caucasus (Armenia, Georgia, Azerbaijan), Eastern Europe (Ukraine, Moldova, Belarus) and Central Asia (Turkmenistan, Uzbekistan, Tajikistan, Kazakhstan, Kyrgyzstan). It was also significant in other Communist countries (mostly in Asia and Eastern Europe, plus Cuba), and in countries previously allied in lesser degrees with the Soviet Union.
If you know Russian, please give us examples and links.
(The author of this stub studied Russian in high school and college, and sang with the Slavyanka Russian Chorus, but is by no means fluent.)