The Apple iPhone 3G has gone on sale today, with queues outside retailers taking up to two hours to get through.

The iPhone is predicted to be a big seller for both Apple and the mobile operators that are offering it. As an indicator of how great this demand is, O2 has been admitting to unit shortages for most of the week, while Carphone Warehouse has also been overwhelmed by its pre-orders.

The iPhone has some new features, but it is the App Store that is the source of some of the more interesting releases. App Store is the firm's platform for software developers and according to the firm more than 500 applications have already been created in time for launch.

“iPhone represents a new software platform for developers, combining the most advanced mobile operating system, sophisticated developer tools and a breakthrough way for developers to wirelessly sell and distribute their applications right onto every iPhone,” said Philip Schiller, Apple’s senior vice president of Worldwide Product Marketing.

One of the applications already in the Store comes from Oracle. Oracle's Business Applications for iPhone are aimed squarely at business users, and, the firm said, will let them work more efficiently, regardless of their location.

The Oracle offering, called Oracle Business Indicators, will let mobile workers access business intelligence applications and information, view financial trends, sales performance indicators, and other related items. Other releases are likely to follow, according to the firm.

Users can browse the available applications through Apple's iTunes store. The Business Section includes the aforementioned as well as a mobile version Of Salesforce.com, and a number of other business-type apps, such as expenses and accounting tools. While British Airways has launched an application which allows customers to access time arrival and departure information, check timetables of flights, and book tickets.