The Rusyn's are the inhabitants of the Subcarpathian Rus a region now known as Zakarpatia in Western Ukraine. It was part of Czechoslovakia before the WWII. According to STRATFOR they are an obscure ethnic group, obscured by the Ukranian state. They strive for self determination and some evidence suggest they are getting moral support from Russia.
Watch this documentary on Russia Today:
And read this report on STRATFOR