If you’re not using one of the supported tumbleblog themes, they have also built a WordPress plugin that will add the tumbleblog functionality. (I may have to take a look at the code one day to see how they have it set up. I assume it probably involves Custom Post Types or Custom Taxonomies somehow.)
I like this idea. It would be great if you could continue to use the normal post type, but add in some mixed media with the tumbleblog plugin (for links and the occasional podcast).