Here is one of my favorite people in the world talking about serial commas and the sometimes contentious "Oxford Comma."
There is a rather loud video ad on this page, so you could turn your volume down.
Here, again, is Grammar Girl. And, again, threre is a rather loud video ad on this page, so you could turn your volume down.
Identifying Incorrect Sentences (fragments, run-ons, and comma splices)
Here is a short article about the dreaded and horrible comma splice. You can listen to the article read by the author by clicking the audio near the top.
Here are online exercises concerning the terrible comma splice:
My apologies for misspelling "difference" in this movie. One day I will correct it and re-record the audio, but I hope you can forgive me if I haven't yet.
Here is the slide show only, without the narration.
Watch out for the loud video ad again!