It seems to be happening quite frequently lately, but the PlayStation Network appears to be out across Australia and the rest of the world as of 3:21pm. It seems to have been down for the last 30-60 minutes with no signs of coming back up.
The PlayStation Network maintenance page states that Account Management, Gaming and Social, PlayStation Video and the PlayStation Store are all experiencing issues. Great news for PlayStation Music fans though, as that seems to be working A-OK.
You may have some difficulty launching games, applications or online features. Our engineers are working to resolve the issue as soon as possible, and we thank you for your patience.