Apple's App Store: 1.8 billion downloads and counting
Right now there are about 75,000 applications to choose from in the App Store, a figure that is much higher than the "merchandise" for sale at other stores like RIM's App World and the Android Market. When Windows Mobile 6.5 is launched October 6th, it will include the Windows Marketplace for Mobile, Microsoft's attempt to join the parade.
Starting with a humble total of 500 apps at launch, the Apple App Store has grown into a real revenue producer for Apple, and some lucky third party developers. It has also changed the course of where the cellphone industry was heading, turning phones into mini-computers and making an on-device app store a feature that almost every smartphone buyer requests.