Several solar system exploration missions routinely publish raw, unprocessed images taken by cameras aboard robotic spacecraft. Unlike most pictures that appear on NASA web sites, these images are not validated or calibrated, and often lack captions and other information to provide context.
What these images do provide is a timely first look at the places where the spacecraft are currently exploring, and a chance for anyone to follow along with missions events almost as soon as they happen.
Following are places to find raw images:
Mars Curiosity Rover - Mars
Mars Exploration Rover Opportunity - Mars
Juno - Jupiter
Cassini - Saturn (Archive - Mission Completed)
New Horizons - Pluto and Beyond