Hot sites/deals and decent freebies at surfer eye level - same as the supermarkets do...
My understanding is a surfer's eye is immediately drawn to the top right of your site - I'm probably wrong lol...
Probably why some of my own favourite blogs have a single left column - and suck for sidebar sales - typical me
I read something about colours too - ones that woo you into buying - guess I should dig that one out - the supermarkets spend zillions on colour specialists