A new option for sellers to expose their products for free: Live Product Upload from Microsoft; From product description:

 What it is
The Live Product Upload, a free service for merchants interested in making their product catalog available in Live Product Search. This easy-to-use gateway is designed to enable online retailers to:

•  Showcase products on  Live Product Search
•  Upload accurate and up-to-date product data directly into the Live Search index

What it does for you
Here is a quick glance of functionality accessible through this service

Catalog Management
Upload you product catalog in any of the formats support, i.e. text or XML through either HTTP upload or FTP. Products can include images, description, price, and links to web addresses on your site.  You can upload any number of catalogs with no specific limits. Once your catalog is successfully published and has passed the validation steps it will be searchable through Live Product Search.

Easy Signup
You will need a Live ID (formerly Passport) to login and signup.  Fill out a simple application that describes your business and optionally fill out more business details.

Reporting
Keep up to date on the status of your catalogs and keep track of your products on Live Product Search.