Here is a 23,040 x 11,520 pixel, color Super Overlay for Google Earth 4. This is meant as a basemap. If anyone would like to contribute additional data (placemarks, etc.) to this, please let me know.

Source: Mars Digital Image Mosaic at 64 pixels per
degree produced at the U.S. Geological Survey in Flagstaff, Arizona

Also, I have a much higher resolution greyscale Mars overlay (Themis IR 256 ppd, whatever that means). Any interest in that? That one has 3 GB TIFF source image (~92,000 x 46,000 pixels) so wasn't going to process it unless there is interest.

EDIT 5/09 - Deleted attachment since its been superseded by Google Mars built into GE.

Matt