TumblRipper is a free small tool created to backup your tumblr pictures to your harddisk. (Or those of a photoblog you enjoy).
Features: StandAlone application (no installation needed). Automatically download all photos from a given TumblR blog. Will try to retrieve the 1280px photo, else 500, 400, 300 or the 250. Only photos you don't already have yet will be downloaded. As light as possible on the tumblR servers (in fact it will cause less load than a normal visitor). Will keep a small text file in the saved directory with the blog url to easily update. Keep the original dates from the original upload.