chyrp.net is the closest to tumblr in UI and functionality. I've tried this and other microblogging wordpress themes in the past and nothing self-hosted really

chyrp.net is the closest to tumblr in UI and functionality. I've tried this and other microblogging wordpress themes in the past and nothing self-hosted really emulates all the features of tumblr/posterous. I like how Tumblr takes care of he little things for the sake of usability and presentation. An example is how Tumblr caches and resizes all posted images to the size of your configured theme.