This is on their facebook site and will only be an online offer
No mention of what is on sale and is mentioned that there will be 16 Exclusive offers
http://i43.tinypic.com/107njbn.jpg
EDIT:
Quote from The Good Guys Facebook :
"There are 16 great items on tonight's Good Night Sale, and amongst them is a 32" Full HD TV, Vacuum, Coffee Maker, Notebook and Washer. So if you're in the market for any of those items pop to the website at 8pm! Happy Shopping everyone!"
nothing interesting on sale.