tumblr2html is an open source app that creates a static HTML copy of a tumblr blog, including uploaded media (like photos).
Just download the sources, and run tumblr2html.py. You will need to have django installed (pip install django) and a tumblr API key, get one from http://www.tumblr.com/oauth/apps
It works, but it should be considered still alpha.
tumblr2html is distributed under the MIT LICENSE.