Firefox/Chrome/IE: Swidget is a browser add-on that swaps banner and box ads for useful widgets, like the weather, news headlines, or even your Facebook feed.
Swidget works on Windows or Mac OS, but only supports Firefox on the Mac. On Windows, Chrome, Internet Explorer and Firefox are all supported. Once installed, the add-on places a button at the top of banner and block ads to click that replaces them with a widget that you choose.
The gallery of widgets is broad: you can choose weather, stocks, clocks, headlines and more. The only downside is that Swidget doesn't work automatically: you have to click to replace each ad on the page one at a time.