don't miss http://www.mapbox.com/blog/cloudless-atlas-with-landsat/ as well

Thanks to Landsat 8 new data also no longer suffers from Landsat 7's defunct SLC

There's also this series of month-by-month cloudless composite maps from NASA: http://earthobservatory.nasa.gov/Features/BlueMarble/

Neat to see things like icecaps expanding and retreating.