For domestic Aussie travel, check whether VirginBlue has any deals to suit you.

The ‘High Tail It’ Sale was advertising fares from $45 all-inclusive (e.g. BNE-NTL) and lots in the $49-59 range, e.g the Tiger routes.  

Check the Happy Hour deals 12-1PM EST, too.

http://www.virginblue.com.au/Personal/Specialsoffers/Specials/index.htm Domestic Flight Specials

Terms & Coditions: see the page above, but generally:

Conditions Apply. [...]