Apple has sent email teasers to all of its ADC (Apple Developer Connection) members, reminding them they still have time to register for the event.

The teaser states:

The Leopard beta. Available first at WWDC.
At the Apple Worldwide Developers Conference, we're planning to show you a feature-complete version of Mac OS X Leopard, and you can take home a beta copy. Be the first to get your hands on the Leopard beta and get a huge head start on development. Register now for WWDC 2007—it's your ticket to the future of Mac OS X.

Registration for the event, which takes place on June 11-15 - has been extended to May 11.

A few weeks ago, the company announced that it would delay the release of Mac OS X Leopard to October, citing need of resources for the finalization of the iPhone which will be released on schedule in late June.

When Steve Jobs introduced the first sneak preview of Leopard during last year's WWDC, he told the audience that some features will remain secret so as to prevent competitors from stealing their ideas.

A few hints on these new features have appeared on recent builds and patent applications, but nothing revolutionnar at the moment. Maybe the most impresseive is the recent patent describing what appears to be a 3D Multiple Dashboard feature.