Southern US slang here are some slang expressions that your are likely to hear primarily in th south-eastern part of the US (where I am from).  

y'all = you all, as in more than one person
"How are y'all doing?"

fixin' to = to be going to do something
"I'm fixin' to go to work."

britches = pants
"Where did you get those britches?"

ain't = am not, is not, are not
"I ain't going to work today."

critter = creature, animal
"I saw some sort of critter in the woods."

purdy = pretty; attractive
"She's purdy!"

reckon = to think; to figure
"I reckon he's not from here."

the sticks =. Far from civilization; far from the city.
"He lives way out in the sticks."

sugar = kiss
"Gimme some sugar!"

tater = potato
"Tonight we're having fried chicken 'n taters."

uppity = conceited; egotistical
"I don't like her, she's too uppity."

over yonder = over there
"That's my friend over yonder."

yankee = person from the northern part of the US, especially the New York area
"I don't fit in with those yankees!"

young'n = young one; a child or baby
"She has 5 young'ns."