G'Day,
There is the non-stop LAX-BNE-LAX offering from Qantas, but as dannyr has pointed to, flying at this time of year is rather expensive.
Thai Airways and Korean Airlines will shortly be increasing services to Brisbane to 5 weekly each. Both offer some good value fares from Australia to the United States so it may be worth looking at these airlines (fly to their US destinations with a cheap fare from your origin).
EVA Airways also service Brisbane (thrice weekly) and have long offered cheap airfares from Brisbane to San Francisco, Los Angeles, New York and Seattle via their Taipei hub.
Air Pacific fly to Brisbane 7 times per week, and have also long offered some very decent and competitive fares from BNE-LAX via Nadi. I'm pretty sure they would offer some good LAX (depart) fares as well.
You've also got JAL, Cathay Pacific, Singapore Airlines, Malaysia Airlines et al, although you have to fly via their respective hubs and flights are much longer.
Unfortunately, Brisbane to Los Angeles (vv) is the only North American non-stop flight from Brisbane, and QF 00175/6 is always heavily booked during the Christmas/Summer Holiday time.
It may pay to look at some of the carriers offering one-stop services from the West Coast of America. I'm sure you could find something good.
Enjoy Brisbane... I'm currently studing at a University in Brisbane. If you need any help with access to Student fares or need any other help, please feel free to email or PM me.
Regards