Android has been making a beeline to the top of the smartphone world for the  last two years, and it looks like the little green OS that could has passed one  of its biggest milestones yet. 
Research  firm NPD says that Android runs on 53% of the smartphones being used in the  US. No other OS comes close, with 
iOS in a distant second at 29%. If mobile  operating systems were horses, Android would lead by about two and a half  lengths.
But the really interesting numbers come in at the third place and lower  contenders. RIM’s 
BlackBerry continues its downward slide with just 8 percent of  the market, and Microsoft’s Window Phone 7 presence is sitting at just 2%.  Compare that to a 50% market share for 
Windows Mobile four years ago. Android  and iOS, the only mobile operating systems making concrete gains, combine for a  whopping 82% of the market. Worldwide Android activations are creeping up on 200  million, beating iOS in just about every market. In some places like the UK and  China, Android reached the halfway point even faster.