If you run ads from networks such as Fastclick or AdSense on your site, a great way to maximize your advertising revenues and promote affiliate offers is to book affiliate banners and links as default ads so that, whenever your inventory has been used up, affiliate ads will instead be showing up.
This is particularly effective with formats such as 468x60 and 120x600 as well as rectangle ads, which are usually included in the body of articles.
Employment911 actually offers a series of 468x60 and 120x600 that can be booked as default ads and new formats should be coming soon.