Eggcorn (en.wikipedia.org)

One I made up as a kid: Very-close veins -> Varicose veins

pleugh

Taken for granite.

Amber-lamps.

Mind bottling.

I lived for several years in the Netherlands and was delighted to learn that the Dutch word for squirrel, "eekhoorn" is pronounced, essentially, "acorn". I'm not aware of any fun-spoiling etymological connection, either.

Someone at work wrote something like "we have achieved parody with <competitor's product>."

While not exactly the same, malapropisms are interesting too :-)

http://en.wikipedia.org/wiki/Malapropism

I have a favorite one of these: "You and me, we're really on the same pagelength."

amber lamps has got to be the best eggcorn of all time

Mondegreens are similar

Nip it in the butt.

Iv'e seen these so much they don't even phase me any more.