The struggling PDA pioneer's smallest, lightest and cheapest ($99) smartphone ever is also one of its fastest selling devices ever. Yesterday, Palm announced the selling of is one millionth Centro, which it first launched back in October in the U.S. with Sprint.

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 in September. “The Palm Centro is flying off the shelves because users who want to step up to a smartphone see it as the perfect first choice,” said Palm senior VP Brodie Keast in a statement.

While Palm has fallen to third place in the U.S. smartphone market, according to Canalysis, it still claims a 9 percent share to Apple's 28 percent and RIM's 41 percent shares. IDC reports 11 percent of all mobile phones sold in the U.S. last year were smartphones. This number is supposed to grow to 35 percent in three years.

Centro is now available in nine additional countries besides the U.S. These include Hong Kong, Singapore, India, the UK, Germany, Spain, Ireland, France and Italy.

Yesterday, AT&T, the second carrier to offer Centro in the U.S., started offering the smartphone in a second color "obsidian black." It had only been selling Cento in what Palm calls "glacier white" since launching the smartphone back in February.