Newest (so-called) 20% off code is FLYNOW. Expires September 18 (although it isn't stated how far in advance one can book).

Did notice that this code had a better than normal deal for parking specifically in the Terminal One garage. For a three-day booking in mid-October the Terminal One garage was $87 (compared to $56 at the Economy garage outside the airport horseshoe). Personally, I am more comfortable parking in the Economy for security reasons and freeway access.