If you want to hit Australia like right now,United is having an unadvertised sale with roundtrip tickets for about $1000, no advance purchase required. For instance, JFK is only $973 with taxes. Usually no advance purchase required tickets cost a pretty penny. The deal is good at airports all across the nation. Qantas is price-matching the sale, too.
Airfares to Sydney (SYD) [AirFareWatchDog]