onethingwell:

Tumblr2WP makes it super simple to transfer your Tumblr content to your own, self-hosted WordPress install.

Or, to put it another way, Tumblr2WP let’s you backup your Tumblr weblog in a format that’s widely used and relatively easy to parse. Unlike Tumblr’s own Mac-only sort-of-backup tool, which (weirdly) hides a potentially useful XML export in a static HTML version of your site.

Tumblr To WordPress Exporter