In addition to Apple's Language Kits, there is a shareware CJK kit for
the Mac.  I've never used it though, so I can't vouch for it.

Most current Mac software should be WorldScript compatible/savvy, which
means you should be able to use other languages with them.  (A notable
exception is anything made by Microsoft.)  You may have to do a little
tweaking.  For example, to use Chinese with Eudora Light, you have to
download an additional tweak.

Another solution is to get the MacOS version localized for the language
you want.  This is probably not ideal if you only know English.

If you're really interested in this, you probably should go to more
Mac-centered sources.

-- Randall M! Gee, Keeper of Gummi Wisdom
(gee@math.berkeley.edu)