Kids Helpline 1800 55 1800
This is a 24/7 helpline especially for australians under 25, so its not just for kids.
Lifeline 13 11 14
This is another helpline especially for suicide prevention and crisis support. Also available 24/7.
Beyond Blue 1300 22 4636
Another great 24/7 help line for problems bug and small, even if you just have a terrible day and need someone to talk to. They also have a great website full of resources and self help tips.
www.beyondblue.org.au
Some other great websites:
www.blackdoginstitute.org.au
www.headspace.org.au