In the latest in a lengthening string of acquisitions, Yahoo! (NASDAQ:YHOO) has bought another niche Internet company. The Internet conglomerate has absorbed Xobni, an email indexing service, according to posts both on Yahoo!'s Tumblr and Xobni's home page. The terms of the deal have not been disclosed, although The Wall Street Journal's  AllThingsD quoted a range of $30 million-$40 million, citing sources "close to the company" that it did not name. 

Over just the past week, Yahoo! has ravenously swallowed several small niche companies. These include Qwiki, a firm that produces an app for Apple's ecosystem that allows users to create short movies and videos from their mobile devices, and fantasy sports app producer Bignoggins Productions.

Fool contributor Eric Volkman owns shares of Yahoo! The Motley Fool recommends and owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.