Google Adsense has enabled content publishers to monetize their sites whereas in the past, there was no capability to do so. While Google Adsense is also prone to abuse by spammers seeking to maximize their earnings by putting up scraper sites filled with Adsense ads, this is otherwise a great method to monetize a site’s content without having to sell a product via affiliate programs or otherwise.
On the heels of the recent Adsense heatmap made available by Google, you can also find an adsense heatmap for forums.
Adsense heatmaps illustrate ideal ad placements on a sample page layout. They are particularly useful to you if you put adsense on a site and need to know where to place the code and what kind of ad layout would be best for optimal results.