When it comes to adsense, there's no replacement for placement. If you check out
http://www.allmags4free.com you'll see a ton of Adsense objects. Most of them get 1-2% CTR which is OK but if you go to a magazine offer, there's a 300px block right beside the exit links and that thing gets over 5% CTR! Try to incorporate differnt object sizes in your website and make them blend in with the rest of your site. You don't want them invisible necessarily, but don't make them stand out as ads. They should just look like other links on your site
