There's a new RFC that defines language codes which should replace
the two part ISO language and country codes (in a mostly upward-compatible
way), I don't have the number handy but it is referenced in the new http
internet draft that just came out. (It was also mentioned a month or
so back in the threads on multilingual stuff, I think.)
A little webbing and gophering reveals that the ISO standard for
language codes is ISO 639:1988. As usual you have to buy this on paper
from the ISO or your national standards body.
Q. Does anyone have it (pirated?) in machine-readable form?
///Peter