Hello

Afrikaans Hallo, Goeiedag
Aleut Aang
American Sign Language http://www.ipl.org/div/kidspace/hello/signlanguage.html
Apache Ya'atay
Arabic Marhaba, Al salaam a'alaykum
Basque Kaixo, Egunon
Bulgarian Ano, Zdrave
Cantonese Neih hou
Cherokee Ohseeyoh
Czech Nazdar, Dobry den
Danish Hallo, Goddag, Hej
Dutch Hallo, Goede morgen
English Hello
Esperanto [a planned language] Bonan tagon, Saluton
Persian (Fars) Salaam
Fijian Bula, Ni sa bula (reply: Io)
Finnish Hei, Paivaa (PIE vah)
French Bon jour
German Guten label, Hallo, Guten tag
Greek Gia, Kalimera
Hawaiian Aloha
Hebrew Shalom
Hindi Namaste, Namaskaar
Hopi Um waynuma
Hungarian Jo napot, Szia (SEE yah)
Icelandic Kalla, Hallo
Igbo Ndeewo
Indonesian Selamat pagi (se LAH mat PAH gee)
Irish (Gaelic) Dia duit
Italian Salve, Ciao
Japanese Konnichi wa
Korean Annyong hashimnikka (AnYOH HASHimnika)
Kurdish Rojbas, Silav
Lakota Hau kola
Lithuanian Laba diena
Malay Selamat pagi
Mandarin Ni hao
Mandinka I be di, I ne ke
Maori kia ora
Mayan Ba'ax ka wa'alik (BAHah shkoWAH ahLEEK)
Mongolian Sain baina uu
Navajo Ya'at'eeh
Norwegian God dag, Hei
Polish Dzien dobry, Czesc /chescha/, Powitanie
Portguese Ola, Bom dia
Punjabi Sat siri akal
Romanian Hallo, Buna ziua
Russian Dobrii den
Samoan Talofa
Scottish (Gaelic) Hallo
Spanish Hola
Swahili Jambo
Swedish Halla, God dag
Syriac Shlom lekh
Tagalog Kumusta
Thai Sawatdii kha (woman speaking), Sawatdii khrap (man speaking)
Tongan Malo e lelei
Turkish Cehennem, Merhaba
Urdu As salaamo aleikum
Vietnamese Chao
Zulu Sawubona (to one), Sanibonani (to a group)

By the way, many of these greetings are for "Good morning".

HELP ME -- if you see something wrong, especially a pronunciation, please feel free to let me know so I can correct it; I will also add languages you think should be in here