It looks like we’ll have to start following World Wind Central as well: The Blue Marble: Next Generation add-on for NASA World Wind turns out to also exists as a KMZ layer (scroll to bottom). What does it do?

Blue Marble: Next Generation offers a year’s worth of monthly [MODIS] composites at a spatial resolution of 500 meters. These monthly images reveal seasonal changes to the land surface: the green-up and dying-back of vegetation in temperate regions such as North America and Europe; dry and wet seasons in the tropics, and advancing and retreating Northern Hemisphere snow cover.

(Via this Google Earth Community post)