Popular social check-in service Foursquare is going through some changes, and the most important of those is that the old v1 API is going dead, as we've known since March. Older apps, especially abandoned ones, will stop working then, as will any newer app that hasn't yet upgraded to the new API.
Factery is a search API with a twist. Instead of links, it returns facts. Actually, it returns links, too. But the real interesting stuff is that it extracts the sentence or two that best answers a user's search.