Users will also have the option of paying for "featured" ads that are highlighted and appear atop search results in a given category. In addition to the individual Tribune sites, the merchandise ads will also appear on the Topix site, which has free classifieds for every U.S. ZIP code. Topix and Tribune will share revenues from the paid ads on the co-branded sites, but did not disclose the split.

Tribune Interactive already partners for other types of online listings with sites such as CareerBuilder, Cars.com and Homescape. Recently, the company decided it was time to upgrade its merchandise listings as well. "We chose Topix because we felt they had a high-quality product and expertise in geo-targeting, and we're also big believers in their network strategy in this category," said Tom Finke, vice president of development at Tribune Interactive. Parent Tribune Company is also one of three newspaper groups, with McClatchy and Gannett, that own a majority stake in Topix.

Founded in 2002, the site collects and organizes news into topics, and allows readers to comment on articles. In addition to merchandise, it also offers classifieds in categories including jobs, autos, and real estate. Classified pages on Topix are monetized by contextual ads via Google's AdSense program.

Finke said the move in part reflects a recognition of increasing competition from free listing sites such as Craigslist, which are forcing newspapers to craft new online ad strategies. Tribune, which also owns the Los Angeles Times and Newsday, had already begun offering free online merchandise listings (for goods below a certain dollar value) in seven of its 12 markets.

He said the rates for featured merchandise ads will vary by market, and that consumers will have to order them through Tribune call centers for the next few months until they can be purchased directly online. Free classifieds placed through Topix will also appear on the co-branded Tribune sites for relevant markets. So a Baltimore area merchandise ad posted to Topix will turn up on the merchandise listings page on baltimoresun.com.

For Topix, it could be the start of more syndication deals. "This is our first foray taking our classifieds technology and moving it off-site," said Michael Markson, vice president of business development at Topix. He added that the company is talking to other newspaper companies, but that no other similar deals are imminent.

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