I've been looking through the AdMob report for April 2010, which includes some of their own stats and other metrics made publicly available.
According to Gartner, iPhone and Android platforms combined to sell 25% of smartphonesworldwide in Q1 2010.
According to Google, 100,000 Android devices were getting activated each day as of May 2010.
According to Apple, 85 million iPhones and iPod Touches have been sold over the past three years as of April 2010.
And here's a great Admob chart of mobile phone market in the US and global.
Source: Admob April 2010 Report