Greeting

Loud sound to get someone's attention:
Ahoy!
Halloo!
Hello!
Hey!

Concern for someone's well-being: 
How do you do?
Howdy ya do?
Howdy!
How are you?
How are you doing?
How you doin'?
Hi ya doin'?
Hi ya!
Hi!
Good day/morning/evening.
Have you eaten? [China]
How are the children? [Massai]
Shalom. [Hebrew for "Peace"]

Pleasure at meeting someone
Good to see you (again).
Your (humble) servant. [archaic]
Ciao. (Italian for "your servant")


Pleasure at meeting someone for
the first time:
I'm delighted to meet you.
Delighted!
Pleased to meet you.
My pleasure.
Charmed (I'm sure) [archaic]

Parting

Concern for someone's well-being: 
God be with ye. [archaic]
Goodbye. [contraction of the above]
Bye.
Bye-bye.
Vaya con dios. [Spanish for "Go with God"]
Godspeed.
A Dieu vous comant [French for "I commend you to God"]
Adieu. [contraction of the above]
Fare thee well. [archaic]
Farewell.
So long ]contraction of "Fare well so long as we're apart"]
Take care (of yourself).
Good day/morning/evening/night.
Have a good/nice day.
Peace.
Shalom. [Hebrew for "Peace"]
Ciao. [Italian for "your servant"]
Cheerio.

Looking ahead to the next meeting:
See you (later).
Until then. 
Auf wiedersehen. [German for "See you again"]
Hasta la vista. [Spanish for "Until I see you"]
arrivederci [Italian for "See you again"]
Toodeloo [from Fench tout l'heure"See you soon"]
Toodles. [Contraction of the above]

Baby talk:
Ta-ta.

You're Welcome

I really don't deserve thanks because it was so easy:
"Aw shucks, 'twart nothin'."
"Don't mention it."
"Think nothing of it."
"Not at all."
"No problem."

I really don't deserve thanks because I enjoyed it too:
"Thank you!"
"My pleasure."
"I was happy to do it."

Noncommittal acknowledgement:
"That's OK."
"Sure."
"You bet."