If you buy a lot on the iTunes store be sure to check out this in store only deal at Future Shop: Get a $60 iTunes Card Multipack (4 x $15 cards) for only $48. That saves you $12 or 20% right of the bat, which is pretty cool.
This was in their national flyer so should be available across the country. The flyer deals end the 11th of August 2011, so you have several more days to take advantage of the deal. :-) I buy all my music and sometimes invest in apps so I love deals like this! These often sell out fast so you might want to call ahead to see if you store has any left.