Sorry, had to do that.
Around since 1554, use of the comma has had a profound effect on language and continues to evolve. Just as I bent the rules in paraphrasing Webster.com's rhyming words and The Banana Song above, we're still doing it with commas. For example, absolute requirement of the final-in-series comma is *still* being debated. (Current standard seems to be play it safe—use it.) Most comma rules are not so wishy-washy; but rather than pontificate on the subject, here is a selection of great links to help you both better understand comma usage and further develop your clients' style sheets. (You know I'm not going to stop nagging about that.) You'll find a lot of other useful tidbits along the way.