This is Garrett Murray's Maniacal Rage

Marco Arment:

Unlike other publishing sites’ approach to backups, our goal was to create a useful copy of your blog’s content that can be viewed on any computer, burned to a CD, or hosted as an archive of static HTML files.

Wherever possible, we use simple file formats. Our backup structure is optimized for Mac OS X’s Spotlight for searching and Quick Look for browsing, and we’ll try to use the same structure and achieve the same benefits on other platforms.

Supports incremental backups and each post file has the Tumblr-API-based XML included so you can do anything you want with the data later. Awesome.