I learned and began to practice the custom of eating black-eyed peas with greens and cornbread on New Year's Day from my Baton Rouge people (thank you, Laura Odom!). I assumed it was a custom of the Southern United States, as it is done all over the South, and because I learned about it from Southern people. It turns out, actually, that folks have been eating black-eyed peas on New Year's Day for prosperity since at least approximately 500 CE, which is when the practice was recorded in the Babylonian Talmud. Sephardic and Israeli Jews practice the custom to this day, on Rosh Hashana.
The Southern connection apparently resulted from the arrival of Sephardic Jews in Georgia in the early 1700s, and the custom spread - as good customs do - beyond the original group of practitioners, and into the general population. In the Southern United States, the peas are typically cooked with a pork product for flavoring (such as bacon, ham bones, fatback, or hog jowl), diced onion, and served with a hot chili sauce or a pepper-flavored vinegar. The traditional meal also features collard, turnip, or mustard greens, and ham.
The peas, since they swell when cooked, symbolize prosperity; the greens symbolize money; the pork, because pigs root forward when foraging, represents positive motion...
I'm going to be all about rooting forward in 2011, people, just WATCH me.
Above liberally adapted from wikipedia.