Gary Price the other day wrote Microsoft's "Google Base" is Code Named Fremont & MS Receives Patent For Semi-Auto Annotation of Multimedia Objects. Basically, Microsoft built a similar application to Google Base, which went live on November 16th.
Today, Microsoft launched http://fremont.live.com/. According to a WebmasterWorld thread named MSN to launch Classified Ad Website, you will need "a @microsoft.com email address for verification."
More articles at eWeek and at RedHerring.