Founder vs. Flounder. Both are good words, that mean similar things but there is a distinction that people mess up.

See: http://grammar.about.com/od/alightersideofwriting/a/floundgloss.htm

Also, people mix up “flesh out” and “flush out”.

I avoid both “flesh out” and “flush out” because the former is a cliche and the latter makes people think of…well, you know

More: http://writeideasmarketing.wordpress.com/2009/04/20/flesh-out-vs-flush-out-either-way-its-disgusting/

Slight puzzle: I was taught that hanged/hung are not interchangeable.
A picture may be hung on the wall, but a person is hanged. I’ve always wondered if that’s actually correct or just blurry historical usage. Does anybody know?

Actually, “beg the question” is a logical term for “circular argument”…but the usage as “prompts the question” or “forces someone to ask the question” has become so popular (due to widespread ignorance and the fact that it sounds as though it makes sense)that it has become acceptable. After all, language is organic, and if incorrect use of the language becomes popular and widespread, by default it becomes correct.

“Probably” has been replaced by “prolly” and “carbohydrate” has been replaced by “carb” and “vegetable” has been replaced by “vege” and it is easy to see why people are disgusted by giving someone “props” or acknowledging that someone has “chops”!

3. ALRIGHT I’m sure I have used this word and was ready to tell you you’re wrong, but after consulting my “grammar bible” — Garner’s Modern American Usage — I will agree. It was listed as a “disputed usage” in my 1988 Webster’s, and according to Garner, while the shortened version has gained what he calls “a shadowy acceptance in British English (where appearances in print are more common)…the combined version cannot yet be considered standard — or even colloquially all right.” So continue to fight the good fight!

12. FARTHER/FURTHER Again, you are correct. To answer one of the comments, while both are comparative degrees of far, they have, indeed, undergone what Garner calls “differentiation” (farther – physical distances, further – figurative distances). However, there is an important distinction to be made on this point. This differentiation is only true for American English. BrE uses “further” as both physical and figurative.

13. FEWER/LESS This battle, unlike alright, according to Garner, “… is probably now irreversible.” Commenters, feel good that you know “10 items or fewer” is grammatically correct, but be prepared for less to continue to “encroach on fewer’s territory” in our lifetime.

26. UNIQUE This is one of my husband’s pet peeves. He likens it to being pregnant – you either are, or you aren’t. And while a third (and disputed) definition of the word is “highly unusual, extraordinary, rare,” which could then take a qualifier like “very,” Garner calls this usage (which apparently began in the 19th century) “slovenly” and a “tendency worth resisting.” Unfortunately, because of the listed definition, this one could be a hard sell in an argument.

Now for two of my pet peeves:
A. The phrase is “first come, first serveD.” The only way it could work as “serve,” is if the first waitress to show up to work got to wait on (serve) customers first.

B. The misuse of “myself” as what Garner calls “an untriggered reflexive” (a substitute for “I” or “me”) drives me crazy. For some reason, people think “myself” sounds more formal or more modest, but it’s really just incorrect when used in this way. The word is best used reflexively (when you have already appeared in the sentence: I hurt myself.) or intensively (I myself have seen that.). And using “myself” certainly doesn’t mean you shouldn’t still come last when listing a group of people. It’s “Rob, John and I are going to the movie” not “Myself, Rob, and John are going to the movie.” This battle seems far from lost. I ask anyone who reads this to please help me by using “myself” correctly in public, as well as “I” and “me.”

I was an English major and I appreciate good grammar. Even so, I do admit to incorrectly using words on many occasions and do not usually correct people. With Garner’s at my side, I edited three of my friend’s self-published books and had a great time both confirming (and sometimes dispelling) my firmly held beliefs. However, I do feel it is important to point out when someone is trying to correct others about supposed “grammatical errors,” when they are, in fact, the ones who are incorrect.

Some comments on the comments:
Unfortunately, @Kelly (post 684), according to Garner, “over” is interchangeable with “more than” and “has been so for more than 600 years.” I know this because I used to correct people on this point, until I realized it was only a style differentiation used by the newspaper I worked for, not an actual grammatical rule.

Thank you, @Bluemoon (post 142), for pointing out that while apostrophes are often misused, there are indeed exceptions to the rule. I had this argument with someone on Facebook recently. Apostrophes most often are used to indicate the possessive (Jane’s appointment) or to take the place of a missing element (can’t). However, Garner states, the third CORRECT usage of an apostrophe is “to mark the plural of an acronym, number or letter” (CPA’s, 1990’s, p’s and q’s). Although the non-apostrophe style is now preferred (CPAs, 1990s), it is important to note that the use of apostrophes in these cases is not incorrect. (Sorry @momo, post 148)

Lastly, if you are reading this, you most certainly will enjoy Garner’s Modern American Usage by Bryan A. Garner. Think of this recommendation as a thank you for reading my comments all the way down here.