After digging around in it a little more, the online Formula and Functions Help seems like a the most complete and handy resource for translation. It can be opened in multiple browser windows like this:

There is not just "translation" of the function names in 34 languages (vs 18 in Ivan Koenig's table), but also the descriptions and examples are provided in each of the languages.
New functions in Numbers 3 include (English ,French, Spanish):
INTERSECT.RANGES, INTERVALLES.INTERSECTION, INTERSEC.INTERVALOS
POLYNOMIAL, POLYNOME, POLINOMIAL
SERIESSUM, SOMMES.SERIE, SUMA.SERIES
UNION.RANGES, INTERVALLES.UNION, INTERVALOS.UNION
WEIBULL, WEIBULL, WEIBULL
SG