Apple has recently added a new listing in the App Store called Top Grossing apps. It appears in the right margin under the listings of Paid Apps and Free Apps. Simply put, the top grossing apps are the ones that are making the most money — an indication of how much they're valued. If somebody's willing to plunk down $9.99 for Call of Duty, the current top-grossing app, it must be pretty good. If you look at the ratings for the top apps in this category, they're typically very high. The Chicago Tribune has posted a handy overview of the top 10 to-grossing apps.