Just checked out the Jetstar web site and there are cheap flights(eg $438.00 return including all taxes) out of Darwin during July school holidays 2009. If you are wanting to leave from Melbourne you can get return flights for $230.00 return. The Melbourne flights marry in with the Darwin flights making the return airfare to Bali, $868.00. Garuda's fare was $1230.00 . If you're a family it is quite a saving.
Cheers Tinggading