On Writing: Won't Someone Think Of The Letters?!

Language is constantly changing. Old words that are no longer useful or fashionable drop from the language, new ones are added, and then we make more up. Spoken language and informal language directly influence formal language. Still, there are some poor, abused letters that end up strung together to create not-words or, worse, to help people who don't pay attention misuse perfectly good words.

Alright
A bastardization of the phrase "all right," this one-word spelling is very common and, these days, seems to be widely accepted. It makes me cringe. Even an attractive, talented man can't make me like this word.

Alot
Hyperbole and a Half has a fantastic post on this word-as-a-thing. This is not a word. It is two words. I distinctly remember devoting an entire week of spelling lessons to this not-word. There aren't even any results for this at Dictionary.com!

Apart (as in, "apart of something great")
Like alot, this word is a commonly-mashed-together not-word. Apart is a real word. It just doesn't mean what people seem to think it means. "Apart" is separate and "a part" is a piece. When you speak, "a part of something great" sounds very much like "apart of something great," so it's pretty easy to see why it ends up written the way it is. This (and the next entry) wouldn't be a problem if the people who make this mistake would simply stop and think about what they're trying to say.

Of for Have (as in, "should of," "could of," "would of")
Yet another victim of spoken language, "of" used in place of the contracted "have" has become far too common. Should have, could have, would have. Should've, could've, would've. "I should of gone to the concert" makes absolutely no sense, but when you say, "I should've gone to the concert" aloud, they sound very much alike. Just looking at the first part of that last sentence makes my skin crawl.

Irregardless
Ir- and -less are both negative, which--according to the double negative rule of English--means that the prefix and the suffix cancel each other out. What this word essentially means is "in regards to" and I have not heard or read this word used in a context that implied "in regards to" was the intended meaning.