Shalom!
!שָׁלוֹם עֲלֵיכֶם [shalom aleikhem] or [shalom aleikhem] - Literally: "Peace upon you!" - this one is the most traditional one, and probably is familiar to everybody, as well as the next one:
!שלום - [shalom] - Most common greeting; but it is in fact simplification of the former. You can also say "shalom, shalom!" Well, I guess, everybody knows what does this mean.
What's up?
?מַה נִשְׁמַע [ma nishma] - "what's up" - is probably second by popularity among the greetings, if not the first.
There is a shortened version of it, it's quite new, and it's rather slang of Tel-Aviv rather than common phrase everywhere:
?מה ניש [ma nish?] I personally think it doesn't sound the best from aestetical point of view... :) But maybe I'm just too old-fashioned...
?מה ניש [ma nish?] I personally think it doesn't sound the best from aestetical point of view... :) But maybe I'm just too old-fashioned...