Today is the day! On FLL's USA website, they have a news bulletin announcing that today at 12:00 (EDT), they will be releasing the 2007 Power Puzzle challenges. From their website:
Challenge Kickoff - Join us here on September 5th at Noon (EDT) for the unveiling of the Challenge. Please note: once the Challenge is launched, it will be available for you to revisit at anytime.
UPDATE: The challenge kickoff has been released, and is available here.
UPDATE 2: Shortcut to the Q&A for official responses to questions here.