Google AdSense has a revenue calculator widget that estimates how much money you can make from Google AdSense on your website. It is not new, it has been around for around a year, but Sunny pointed it out to me on Twitter a few weeks ago.
You can access this widget on google.com/adsense/start and scroll down the page a bit until you see this section:
Of course, I would not expect to make as much money as the widget estimates. You should know it is a marketing tool for AdSense.
Either way, this has been around for about a year and it is a smart tool to add to the marketing page. I just don't know many people who make a lot with AdSense these days, of course, most people I know are smaller publishers.
Forum discussion at Twitter.