Russian

To use Russian in ConTeXt MkIV, you need a font that has cyrillic letters, e.g. the DejaVu fonts which are shipped with the ConTeXt Standalone.

\setupbodyfont[dejavu]

\mainlanguage[russian]

\starttext
Немного русского текста для пробы.
\stoptext

For more details on how to change fonts in ConTeXt, see Fonts in LuaTeX