The next examples show how to use a colon to introduce a list:
There are three countries beginning with Z: Zaire, Zambia and Zimbabwe.
The nightclub played many different types of music: rock, hip-hop, electronica, indie and even soul.
These following examples show how to use a colon just to introduce a single item:
The role of the colon is simple: to introduce.
We knew who would be first in the race: speedy Steve.
The next examples show how a colon can introduce speech:
She grabbed the microphone and asked: “Is there a doctor in the house?”
Kate whispered in my ear: “Haven’t you got a PhD?”
As Julius CaesarĀ once said: “We came, we saw, we conquered.”
Further examples show the colon used to introduce an explanation:
He asked why I hadn’t said hello: I hadn’t seen him.
Don’t bother coming over anymore: I’m not feeling well enough to meet up.
Read more about how to use the colon.

Some terrific examples of how to use this sadly neglected punctuation mark. Bravo!
I love the examples on this site. So much better then the usual boring ones.