Apple announced that more than 100,000 developers downloaded the iPhone beta SDK in the first four days since it launched last week.

“Developer reaction to the iPhone SDK has been incredible with more than 100,000 downloads in the first four days,” said Philip Schiller, Apple’s senior vice president of Worldwide Product Marketing, in a statement. “Also, over 1 million people have watched the launch video on Apple.com, further demonstrating the incredible interest developers have in creating applications for the iPhone.”

Along with the iPhone SDK, Apple also previewed the new App Store, a new portal on iTunes allowing users to download newly developed applications to their iPhone or iPod Touch. Developers set the price for their applications, including free applications, and then receive 70% of sales revenues.

Apple says that leading developers such as AOL, Electronic Arts, Epocrates, Salesforce.com and Sega already have demonstrated applications using the SDK and the company expects developer enthusiasm to continue.

The free beta iPhone SDK is available immediately worldwide and can be downloaded at developer.apple.com/iphone/program. The iPhone Developer Program will initially be available in the United States and will expand to other countries in the coming months.