This great site:
http://www.itunesonsale.com.au http://www.giftcardsonsale.com.au/ (it’s been renamed due to a legal battle with Apple) is regularly updated and lists iTunes card specials from around Australia. For example it currently lists that you can currently get 25% off iTunes cards at Big W and the Good Guys. That means 25% off Apps purchased from the new Apple App store. 25% off Pages, 25% off Keynote, 25% off Aperture etc.
Yes, I just used relative rage is in the last year.