News aggregator Topix.net quietly added a free classifieds feature to its site around a month ago, and some 300 listings are being added each day, reports ClickZ. The company expects to monetize the service with ads, as well as eventually syndicate them via partner sites.

The classified listings appear only on local news pages when users search for stories by ZIP code or locality. The Topix.net system features only listings submitted by users, not those from other classified sites. The system allows users to display photos with the listings that appear in pop-up windows.

Google's contextually targeted AdSense ads accompany Topix.net's classified listings and other content. Currently only geo-targeted, they might be organized by vertical.