Along the right side, next to the main menu [specified area shown in the image on the left, showing Apple Store ad] -- Images must be 120px or less in width and 240px or less in height. The rate is $49.95 per month.

Along the bottom of sidebar [specified area shown in the image on the right, where the Apple ad is located]-- Images must be 234px or less in width and 300px or less in height. The rate is also $49.95 per month.