People:

Oppa (오빠) -- Affectionate way for a female to address an older boy

Eonni/Unnie (언니) -- Affectionate way for a female to address an older girl

Hyung (형) -- Affectionate way for a male to address an older boy

Noona (누난) -- Affectionate way for a male to address an older girl

Eomma/Umma (엄마) -- Mum

Appa (아빠) -- Dad

___-sshi/___-ssi (__-씨) -- Formal way of addressing somebody

Ahjumma (아줌마) -- Auntie (does not have to be related. Can be used to address another lady.)

Ahjussi (아저씨) -- Uncle. (does not have to be related. Can be used to address another man.)

Greetings:

Annyeong (안녕) -- Hello/Goodbye (informal)
Annyeonghasaeyo (안녕하새요) -- Hello (formal)

Komawo/Gomawo (고마워) -- Thank you (informal)
Kamsahabnida/Gamsahabnida (감사합니다) -- Thank you (formal)

Mianhae (미안해) -- Sorry (informal)
Mianhaeyo (미안해요) -- Sorry (formal)
 

Saranghaeyo (사랑해요) -- I love you

Any questions can be asked here and I will do my best to answer you. :)
More words will be added to this list when I think of them :P

And if you are curious, no I am not Korean. :( I do speak basic Korean and I have quite a number of Korean friends. :)