The concept is almost identical. Decide on three tags your tumbleblog fits into (eg. music, photography, design), complete the form and that’s all there is to it.
The blogs are order by ‘tumblarity’ (popularity), and I must admit I’m rather impressed with the number of subscribers some of the tumblr’s have.
Tumblr founder David Karp points that the directory will be in beta for approximately two week and until then you’ll only be able to select two tags from their current selection.