If you're looking to top up on prepaid Skype cards, paying full price would be a bit silly. Coles, Woolworths and Target are all currently selling both the $10 and $25 varieties for half the recommended retail price -- $5 and $12.50 apiece.
The Skype cards can be used to pay for monthly calling plans or casual access to landline/mobile phones. The $10 and $25 cards provide up to 400 minutes and 1000 minutes of calling, respectively. [Via OzBargain]