There are several areas of your website which are considered 'hot spots' for advertisements such as affiliate programs or google adsense. These spots include the top left of your site, just under your title, the left hand side of your page, and between posts. Unfortuneately, users frequently develop ad blindless when viewing a website: they learn to ignore your ads because they know the location has no relevant information to them.
How to you avoid ad blindness? Move your ads around! That's right, change it up a bit and watch the increase in hits that you get on your google adsense or other ads. You should notice a sudden spike from users who normally would not view your ads but now are taking a glance at them since they are in a new location.
This has worked like a charm on my websites and I tend to do this about once a month to avoid causing a headache for my more frequent users.