My kids got a kick out of this site!
Cow
Afrikaans: moe-moe
Albanian: mu
Arabic (Algeria): mooooooo
Bengali: hamba
Catalan: muuuu
Chinese (Mandarin): mu mu
Croatian: muuuu
Danish: muh
Dutch: boeh
English: moo
English (Old English): Oxa hlewð.
Esperanto: muu
Estonian: muu
Finnish: ammuu
French: meuh
German: mmuuh
Greek: moo
Hebrew: moo
Hindi: mo:-mo:
Hungarian: bú
Icelandic: mu
Italian: muuuuuu
Japanese: moo
Korean: um-muuuu
Norwegian: mø
Polish: muuuuu
Portuguese: muuuu
Russian: muu
Slovene: muu-muu
Spanish (Spain, Argentina): muuu
Swedish: muu
Thai: maw maw (with mid tone)
Turkish: mooooo
Ukrainian: muuu