ABA has an excellent member discount freight deal with digital freight management company Couriers and Freight.
Couriers and Freight is a comparison site that allows users to compare rates across multiply providers and then make pay as you go bookings. Users can either use the service for 'one-off' bookings or set up a pay as you go account with additional features such as stored addresses and reporting. The website is backed up by a IRL customer service team that can assist with bookings.
This service is ideal for sending multiple box returns to publishers or for smaller packages when Australia Post delays are a concern.