A guide to Android: Diversification amid swift growth

According to NPD Group, Google's Android mobile operating system now represents 28 percent of smartphone unit sales in the U.S.--behind only Research In Motion's BlackBerry (36 percent) and moving past Apple's iPhone (21 percent). Analysts agree the evolution of Android is not likely to slow down any time soon. This guide looks at the major Android devices released (with prices) for the U.S. market, with an eye toward their pros, cons and market impact.