In April Google allowed free listings within the Google Shopping tab and then expanded it to the main Google web search results. Bing seems to be following suit and allowing free product listings in the Bing Shopping tab of search. But those free product listings may go unseen since they seem to be placed in the footer.
Bing announced "we’re excited to announce the availability of free Product Listings, which allow you to show your product offers for free on the Bing Shopping Tab starting in the USA and soon rolling out to other markets — United Kingdom, Canada, Australia, France, and Germany."
Here is a screen shot Bing provided showing the product listing ads take up virtually the whole page with the free listings in the footer:
Product Listings are currently offered to those who have a Microsoft Merchant Center store with approved offers, and will ramp over the next month, Bing said.
To enable this, there is nothing you need to do if you are a Microsoft Shopping Campaigns customer. By default, all approved product offers in Microsoft Merchant Center will automatically be opted into this new offering. But if you are not a Microsoft Shopping Campaigns customer, create a Microsoft Merchant Center store, submit all eligible products, and ensure they’re approved. When the Merchant Center store is created you’re opted-in to the free Product Listings offering, enabling your approved products to be eligible to show in the free products listings section on the Bing Shopping Tab.
Forum discussion at WebmasterWorld.