Quoted from Giardiasis:

I think this should pretty much cover it, in every possible language.
WELCOME!!!!!
Afrikaans Welkom
Albanian Mirë se vjen
Aleut Qaĝaasakung huzuu haqakux̂
(Thank you all for coming)
Alsatian Wellkumma
Willkumme
Amharic እንኳን ደህና መጣህ- i'nkwuan dehna metah (m)
እንኳን ደህና መጣሽ- i'nkwuan dehna metash (f)
Arabic
(Egyptian) (ahlan wa sahlan) أهلاً و سهلاً
Arabic
(Lebanese) Ahla w sahla
Arabic
(Modern Standard) (ahlan wa sahlan) أهلاً و سهلاً
Aragonese Bienveniu / Bienvenius
Armenian
(Eastern) Բարի գալուստ! (Bari galu'st)
Armenian
(Western) Բարի՜ եկաք: (Pari yegak)
Aromanian Ghini vinit! (plural) Ghini vinishi! (singular)
Assamese আদৰণি (aadaroni)
Asturian Bienveníu / Bienvenida
Azeri Xoş gəlmişsiniz!