Lot's of the biggest, best images are no longer on nasa. What used to be free is now content on google earth, Universe or other apps that pay money.
A good but hard to use resource is.
ftp://pdsimage2.wr.usgs.gov/cdroms/clementine/Clem_NIR_V0.1/A_welcome.htm
There are some good images mixed with a lot of unusable ones.