Have a look at pages like these to give you ideas on peoples eye movement around websites. http://poynterextra.org/eyetrack2004/main.htm http://psychology.wichita.edu/surl/usabilitynews/71/eye_tracking.html http://www.enquiroresearch.com/eyetracking-report.aspx
Great links Wardy, very useful info there. So it seems that placing a big picture adsense ad (250x250 or bigger) on the right of the main content is the probably the best placement strategy. Trouble is that adsense pictures ads are a lot lower than the text ads, so maybe an affiliate link there instead? BTW does anyone do picture ads with adwords and use the content network?
content is very important. if your site is for webmasters, ads placement is not important a lot. but if it is a magazine blog, ads in content and using top menu ads will get more clicks.