How many Nintendo DS units have been sold?

128.89 million.

The report “Earnings Release: Fiscal Year ended March 31, 2010”, issued in May 2010 by Nintendo, announces that 128.89 million Nintendo DS units have been sold since its release, in 2004. Japan is the top country in DS sales: over 3 million units; in the American continent, over 4.6 million units have been sold.