Insure, Ensure, Assure

Examples:

All three are interchangable, however with "insure" you'll
take necessary steps beforehand, like "I'll insure my car".

With "ensure", you'll guarantee something, making it safe,
i.e. "The safety of the children is ensured".

To "assure" something: remove doubt from someone.
"I'll assure my creditors that I will pay".

That would be my interpretation

Hardly interchangeable. Three different words with three different meanings as CJ noted.

"Insure" and "ensure" can be used interchangeably when used in the general sense of "to make sure" or "to guarantee." "Insure" also has the additional meaning of "to provide insurance."

"Assure" also has the meaning of "to make sure" or "to make certain," which would make it a synonym for both "insure" and "ensure." It also has the connotation of "removing doubt." Typically, one sees "ensure" in connection with things, "assure" in connection with people.

examples
"I ensure that this machine will operate properly."
"I assure you that this machine will operate properly."

Nevertheless, that is not a hard-and-fast rule. Indeed, the terms "assurance" and "insurance" can also be used interchangeably (the former, I believe, is more common in the UK than in the US). So there is a lot of overlap between the three terms; luckily, they mean roughly the same thing, so the risk of confusion is minimal.

I stand corrected, joe,
But to me...three distinct words.