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[Microsoft] Listas is, put simply, about making lists. Users can make their own lists, by either typing in original content or taking clippings from Web pages, or they can read or edit public lists. The lists can include almost any type of content, including images and videos. They can be designated either public or private, and they can be tagged to make them easier to search.
Like other social-networking sites, Listas also allows users to acknowledge each other as "friends." A user's lists, lists made by his or her friends, and public lists that the user has linked to are all collected on a single page on the Listas site.