Update: This deal also seems to work for Melbourne and Brisbane and from additional U.S. cities. See the Secret Flying link below for the latest.
Virgin Australia currently has a great deal on flights from either San Francisco or Los Angeles to Sydney, Australia. Flights for various dates in August and September, 2016 are pricing out for as low as $416 roundtrip.
To find the deal, search for flights on Momondo and then click through to book with one of the OTAs.
For more info about how to search and which dates will work, see this Secret Flying post.