Check out this Adsense case study at Google of Weblogs Inc. (the company that was purchased by AOL for $25 million last week.)

After implementing AdSense, Weblogs blogs were earning only a couple hundred dollars a day from the program. “At first we didn’t really understand how to use it,” Calacanis says, noting that “we thought of it as helping to pay some bills.” But when over about six months’ time AdSense revenues reached more than $1,000 a day, he says he realized that there was a significant opportunity in AdSense – if his team would invest the time in making it work even better.