There are plenty of colorful Southern phrases around (for samples, try this cleverly named and hilarious SouthMouth collection), and I enjoy hearing them, but I particularly enjoy the ones that I would describe as Southern grammar.
Many people, including some very highly educated folks, use these expressions in casual communications, both spoken and written. We are friendly here in the South,* and maybe we take a little more time with our daily routines than other folks; including a few extra words that add meaning is one of the ways we show that.
Here are a few little pearls I've heard recently:
Who all - the plural of who, as in "Who all is going to this?"
All y'all - when y'all isn't expansive enough. In the South, there's you, meaning you alone; then there's y'all, meaning you and a few others, and all y'all, meaning you, your whole family, and all your friends. As in, "I'd love for all y'all to be there."
Might oughta - favorably considering a possible course of action, as in "With all this rain lately, I might oughta start building an ark."
Fixin' to - preparing to do something, as the first step in actually doing it. As in, "I'm fixin' to start dinner, just as soon as I finish my drink."
*It could be argued that Florida is not the South, because so many of its citizens are from elsewhere. That said, Southern culture is still pretty strong here, especially in the northern half of the state and in rural areas. It could also be argued that because of the phenomenon known as Weird Florida, we exist in a category all our own.