To display all the languages that Emacs is capable of displaying, you will require the BDF fonts from the GNU intlfonts package. See How do I use bdf fonts with Emacs?.
For many languages, native truetype fonts are sufficient, and in Emacs 23 the need for BDF fonts will disappear for almost all languages. At the time of writing, all supported characters are able to be displayed with appropriate truetype or opentype fonts.