The Oxford Comma
I am a big fan of the Oxford comma. What is it, you ask? The Oxford comma, also known as the "serial comma", is an optional comma before the final "and" at the end of a list.
It just makes sense. The Oxford comma allows us to write more in the cadence in which we speak. It puts a natural pause before the last item in a list. To leave out the final comma in a list allows greater room for misinterpretation. This can happen easily in written work since you don't have the added benefit of being able to view and comprehend the writer's body language.
For example, I might write, "I went to the farm to play with the pigs, Carol, and Julien." By using the Oxford comma, I have let the reader know that I went to the farm to play with three different entities. If I delete the final comma, the sentence would look like this, "I went to the farm to play with the pigs, Carol and Julien." With this version, it's quite possible that I have offended Carol and Julien by implying that they are pigs.
For some amusing images highlighting why the Oxford comma is important, click here.
Fans of the Oxford comma even have a Facebook page. (Yes, I've "liked" it.) You can check it out here.