Apple has released a new version of its iPhone SDK for developers, iPhone SDK beta 2.

According to Apple's own notes, the release includes Interface Builder, which the company calls "a powerful tool that allows you to visually build your interface and makes creating a user interface as simple as drag-&-drop."

"We've also added new sample code and updated documentation to the rich set of resources available to you in the iPhone Dev Center." the company explains.

Apple unveiled the iPhone SDK at a special event earlier this month, allowing developers to begin building applications for the iPhone and iPod touch.

The free download is available online through the company's Apple Developer Connection website. Apple plans to upgrade the devices' firmware in June to enable third party applications developed using the SDK to run on an iPhone.