Centro, Palm's smallest, lightest and cheapest ever, is continuing its best-seller ways. A few months ago, the PDA pioneer shipped its millionth Centro unit. It has now surpassed the 2 million mark.

Palm is now offering Centro in more than 25 countries in North America, South America, Europe and Asia Pacific, through 20 mobile operators, including the top-three U.S. carriers (AT&T, Verizon, & Sprint).

Centro has proved particularly popular among those stepping up to a smartphone for the first time. According to Palm, for 75 percent of those who buy Centro, it is their first smartphone. This is the very type of user Palm said it was targeting when it first announced Centro last September.

Recent data released by AdMob, the largest advertising network on the mobile Web, states that Centro is among the top 10 devices worldwide for mobile Internet. AdMob cites the growth of inexpensive phones, such as the $99 Palm Centro, which can be had for as low as $69.95 from AT&T now, as a primary driver in mobile Internet usage.

AdMob also analyzes worldwide data to gauge mobile Internet use among devices able to receive mobile ads. It notes that 24.3 percent of worldwide ad requests in June were from smartphones, up from 22.4 percent in May.

For more on Centro, see links below.