Apple has seeded the seventh Developer Preview of OS X Mavericks to developers



From MacRumors:

Registered developers can receive the update via the Software Update tool in the Mac App Store. OS X Mavericks, which is expected to be released this fall, includes multiple new features like a tabbed Finder, full screen dual monitor capabilities, Safari improvements, and a new Maps app.

  Apple Releases OS X Mavericks Developer Preview 7