I know that the official Associated Press style is to omit the serial comma. Personally I prefer it, but surely it's found both ways.

Also, the New York Times stylebook recommends against the serial comma.

My wife is a technical editor, and ommitting that last comma is one of the things she enforces.

Okay, but does she enforce doubling the 'm' of 'omit' too? :*)

No, it was just early in the a.m.

Heck, even if Safire had included the comma, the copyeditor would have excised it.

I had quite a dustup with Colby Cosh about this - he calls it the "Oxford comma" and I don't like it. But he'll give you an argument about it.

I prefer the presence of the comma, on the idea that punctuation signals mannerisms of speech and someone reciting a list would pause before the "and" following the penultimate item in the list. But I do not insist either way, nor do I pay heed to those who insist it must be one or the other, present or omitted. I simply assume those who insist it must be omitted have never read aloud, and those who insist it must be present have never hand-set type.

On a similar topic, I actually vary in my own writing about the rule that if a sentence ends with a parenthetical clause/expression the punctuation must go inside the parenthesis. Sometimes I do, sometimes not. When the matter inside the parentheses is not in keeping with the sentence as a whole, I may even do both -
"(...?)." or "(....)?"
which horrifies some: tough.

I was taught that the ultimate comma was a good idea in order to avoid the kind of confusion illustrated by this example:

"I would like to thank my parents, God and L. Ron Hubbard."

If one's parents were God and L. Ron Hubbard, that sentence would read: "I'd like to thank my parents: God and L. Ron Hubbard."

God forbid one of my parents should be L. Ron Hubbard.

I like the serial comma. I think it makes the groupings more clear.

I believe the usual version is "my parents, Ayn Rand and God", not L. Ron Hubbard.

Hmm, maybe my teachers in Punctuation 1A thought L. Ron would be less controversial than Ayn - or funnier.

It is called the Oxford Comma (that's not a Colby Cosh thing). It's also known as the Harvard Comma or the Serial Comma. It is less common in British writing, and more common in American writing. Originally, it was mandatory. Later, newspapers began to leave it out (I'm told for reasons relating to the monospaced fonts necessary on old typesetting machines). That's why the AP and the NYT leave it out.

The better practice is to use the comma. Aside from the examples listed, there are numerous circumstances where the comma is necessary to avoid confusion.

"Mom served macaroni and cheese, peanut butter and jelly, and milk for lunch.

Compare:

"Mom served macaroni and cheese, peanut butter and jelly and milk for lunch."

Here's a more realistic example: If you were to write “He studied Roman history, international politics and economics” it is not obvious whether international refers only to politics or also to economics.

Because there are examples where use of the comma is absolutely necessary to avoid ambiguity, it is better to use the comma all the time, rather than to use it inconsistently (and give the appearance that you just don't know either rule).

The serial comma removes ambiguity. Eliminate the serial comma, and you are left with sentences like:

"I would like to thank my parents, Ayn Rand and God."

Google says that Rand beats L.Ron ~147 to 10, including comments on this blog. I've heard the Rand version several times but I'd never heard the alternate before.

We were taught to omit the terminal comma except where ambiguity would arise.This was at a private school in the UK in the '70's. I think the general lesson to be drawn is that there is no substitute for reading what you have written.

As Sir Ernest Gowers says, "The use of commas cannot be learned by rule ... The correct use of the comma—if there is such a thing as "correct" use—can only be acquired by common sense, observation and taste."

His guide to this particular case states:

"In such a sentence as:

The company included Ambassadors, Ministers, Bishops and Judges.

commas are always put after each item in the series up to the last but one, but practice varies about putting a comma between the last but one and the and introducing the last. Neither practice is wrong. Those who favour a comma (a minority, but gaining ground) argue that, since a comma may sometimes be necessary to prevent ambiguity there had better be one there always.

Supposing the sentence were:

The company included the Bishops of Winchester, Salisbury, Bristol, and Bath and Wells.

the reader unversed in the English ecclesiastical hierarchy needs the comma after Bristol in order to sort out the last two bishops. Without it they might be, grammatically and geographically, either (a) Bristol and Bath and (b) Wells, or (a) Bristol and (b) Bath and Wells. Ambiguity cannot be justified by saying that those who are interested will know what is meant and those who are not will not care."

Those who might like to read Gowers' classic The Complete Plain Words, the essential guide to clear yet elegant English, can find it here.

So, has anyone thanked their parents, Ayn Rand and L. Ron Hubbard?

I think there's someone who would work even better than Ayn Rand or L. Ron Hubbard:

"I would like to thank my parents, Madonna and God."

Reasons against the final serial comma:
When a series is not ambiguous, it saves space.

Reasons for the final serial comma:
It eliminates ambiguity and maintains consistency.

If consistency is important to your writing or your organization's writing, which I should hope it would be, there clearly is no argument. The "Fors" have it. Consider the following:

I took courses in political science, corporate accounting and tax laws.

To maintain consistency, no comma before the "and" in the example above would in fact be correct if one took a single course in corporate accounting and tax laws. Adding the comma would then signify that corporate accounting and tax laws were two separate courses.

"I took courses in political science, corporate accounting, and tax laws."

I'd like to thank my kids, Jesus and Moses.

It strikes me that, if we were to credit the author with a general tendency to avoid ambiguous constructions, we would indeed expect said author to write "My parents: Ayn Rand and God," as opposed to "My parents, Ayn Rand and God" if what the author really intended was to reference his divine/objectivist heritage. However, because I like the example, particularly in its admonitory function, I would like to point out that it could be rescued by being placed in the first of a stacked pair of subordinate clauses, thus:

It went against the tenets of my parents, Ayn Rand and God, tenets I held most dear, but I simply couldn't shake the feeling that sometimes, "A" isn't "A."