The Mac OS itself will run in any language under on this planet without additional language packs, unlike windows. Depending on the Application, you may be required to purchase the application in the language of choice. Having said that, some give universal support.
MacOffice 2004 English international version, has dictionary support for just about any language. Although the application interface is, i think in English only. If you want it in French I think you'll need a French version.
A standard keyboard has support for All European languages. To access é ü î à or any of the accents, you just press option (alt) key.
Personally, I wish Apple have keycaps for a Chinese keyboard...