With today’s Unicode enabled TeX engines you could use TeX to typeset books in Russian or Classical Greek or any language. So you need hyphenation patterns for a lot of languages, converted to UTF-8. The file hyphenation.pdf (→) lists all hyphenation patterns for TeX, which have been collected in a single package hyph-utf8, which can be used in pdfTeX, XeTeX, or LuaTeX.
An example of their use is given in the following files: hyph.tex, hyph.pdf
These files use the commands \uselanguage{ukenglish}, \uselanguage{ngerman}, etc to switch between hyphenation patterns. If you find those commands a bit long, you can create an alias like this: \def\de{\uselanguage{ngerman}}; now \de will apply German hypenation.
There is another method which allows more control over the hyphenation:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
These macros written by Karl Berry allow you to change the values of
% for hyphenation profiles and European languages
{\catcode`@=11
\gdef\eplainsetlanguage#1#2#3{%
% do not set the language if the name is undefined in the current TeX.
\expandafter\ifx\csname lang@#1\endcsname \relax
\message{no patterns for #1}%
\else
\global\language = \csname lang@#1\endcsname
\fi
% but there is no harm in adjusting the hyphenmin values regardless.
\global\lefthyphenmin = #2\relax
\global\righthyphenmin = #3\relax
}}%
\def\ukenglish{\eplainsetlanguage{ukenglish}{2}{3}}
\def\ngerman{\eplainsetlanguage{ngerman}{2}{3}}
\def\russian{\eplainsetlanguage{russian}{2}{2}}
\def\latin{\eplainsetlanguage{latin}{2}{2}}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\lefthyphenmin and \righthyphenmin. \lefthyphenmin sets the minimum number of characters before a hyphenation, \righthyphenmin the minimum number of characters after a hyphenation. \lefthyphenmin is normally set to 2 and \righthyphenmin to 3, so the word ‘advocate’ could be broken ad- vocate or advoc- ate but advoca- te would not be permissable. The 2, 3 settings seem to be used in English, French and German. But other languages may have different settings.
Also in \def\ukenglish{\eplainsetlanguage{ukenglish}{2}{3}} the \ukenglish can be changed to something different if you prefer, e.g.
\def\english{\eplainsetlanguage{ukenglish}{2}{3}}
\def\deutsch{\eplainsetlanguage{ngerman}{2}{3}}
\def\rus{\eplainsetlanguage{russian}{2}{2}}
\def\francais{\eplainsetlanguage{french}{2}{3}}
\def\gaeilge{\eplainsetlanguage{irish}{2}{2}}
Here is the example file above but using the Eplain hyphenation macros. I’ve also tested the hyphenation a bit more by setting the type in two columns using Eplain’s \doublecolumns macro: hyph2.tex, hyph2.pdf
Of the two methods the first is easier to use. It also works better when used within macros.