“What's Popular” is an iGoogle gadget that highlights popular content from the web. Much like Digg, Reddit or Yahoo Buzz, you can vote the web pages and add content you find interesting. Right now, the most popular web page has 13 pops (probably a name for upvotes), there are three categories: stories, videos, images and the pages are sorted by relevancy, the algorithm favoring recent content.
More info: What's Popular
Source:→ Google OS