Aussie Broadband are offering 1 month free on their NBN plans. No lock in contracts. I don't see anything about it being for new customers only but I assume it is.
Deal excludes nbn™ 150, nbn™ 250 and enterprise plans.
For those searching for a new NBN don't forget the other OZB favourite provider Superloop
Hmm might be time for me to jump ship and give superloop a try