accede, exceed

Accede means to agree, to allow; exceed means to go beyond, to surpass, as in
“Drivers who exceed the speed limit are asking for hefty fines.”
accept, except

Not commonly seen even from unpublished writers, who are probably familiar with the difference because they’re all waiting for an acceptance!
“We accept your invitation to your party, except for Bill, who will be away on that day.”
However, I recently saw (on a publisher’s web site!) the statement, “We are excepting submissions … ” Can you believe it?

adapt, adept, adopt

Adapt means to adjust, adept means skilled and adopt means to take as your own:
“Some people cannot adapt to new surroundings.”
“He is very adept at dodging awkward questions.”
“He tends to adopt the attitudes of those around him.”

addition, edition

I saw this confusion on a review on amazon.com—“a nice edition to the series”. Obviously the writer meant addition. However, if one person can get these confused, maybe others do too. Addition is something that is added; edition is a particular version, issue or publication of a book, play, etc.
adverse, averse

Adverse means inauspicious, hostile; averse means disinclined, repelled.
“I’m very much averse to making a long, arduous journey under such adverse weather conditions.”
advice, advise

Advice is the noun and advise the verb.
“His advice was that we should advise everybody to either stay away or be extremely careful.”

affect, effect

Affect is a verb; effect is more usually a noun. When used as a verb it means to achieve, fulfill, realize.
“Bad weather will affect the quality of the fruit.”
“The effect of bad weather is a reduction in fruit quality.”
I can’t think of any sentence using effect as a verb where one of the other three mentioned above would n’t be a much better choice, but perhaps a politician might say, “To effect our goal of saving 10%…”
aloud, allowed

Aloud means out loud, speaking so that someone else can hear you; allowed means permitted.

altar, alter

Altar is the table in a church; alter means to change.

already, all ready

Already means by this time; all ready means prepared.
“Are you already packed?”
“Yes, I’m all ready to leave.”
altogether, all together

Altogether means wholly; all together means everybody in a group:
“It’s altogether too bad that you can’t come.”
“All together, now: ‘Good morning, Sir!’”
all right, alright

All right is the correct form; alright is grammatically incorrect.
allude, elude

Allude means to refer to; elude means to dodge or escape.
allusion, illusion

Allusion is an indirect reference or hint; illusion means deception or mirage.
all ways, always

All ways means by every way or method; always means all the time, forever.

amoral, immoral

amoral describes someone who has no morals; immoral describes someone with low morals.

annual, annul

Annual means yearly; annul means to make void or invalid.
anyone, any one

This is quite tricky. Anyone means anybody, any person at all; any one means any one person and is followed by “of”.
“Does anyone else want to come?”
“Any one of you is welcome to come along.”
appraise, apprise

Appraise is to assess or estimate. Apprise is to inform or notify:
“I will appraise the situation and immediately apprise everybody of my conclusions.”
Please don’t make your character say or write anything like this, though—unless you want him to sound like a pompous twit!
ascent, assent

Ascent is an upward movement; assent means agreement.

assistance, assistants

Assistance means help or aid; assistants is the plural of assistant, one who gives help.
assure, ensure, insure

Assure means to guarantee; ensure means to make sure; insure means to protect against loss or damage:
“I assure you there’s no call for alarm.”
“To ensure your crockery does nt get broken, wrap it all in bubble wrap.”
“In case of breakage or loss, you should insure everything with a good insurance company.”
auger, augur

Auger is a tool; augur means to predict.