Hello, I'd like to help. There are a few possibilities for what your saw, depending upon where you live in the United States.One possibility is a Black Milk Snake: The other is a Ribbon Snake:
Neither snake is poisonous and both will try to escape if they can, but will bite if they are picked up and frightened as a defense.Let me know if you have further questions.
Since you are in Australia the first possibility is the Moon snake or orange naped snake. Mildly Venonous, but not considered a threat to humans: http://www.snakesofthewhitsundays.com/elapids/orange-naped-snake.shtml
The other possibility is a Gold Crown snake:
This is also mildly venomous, but not a threat to humans: http://www.snakecatcher.com/goldencrownedsnake.htm
If these are not what you have seen, please let me know. Australia has the greatest amount of venomous snakes and it is important to identify what you had seen. Joan