I never signed up for the "real" tumblr because I wanted to host this myself, and I thought it would be nice to hack at it if necessary. So I was running Gelato CMS which seemed like the best open-source PHP tumblr clone. It became apparent that the developer of Gelato wasn't going to develop it any further and a few things had stopped working (due to changes in YouTube and Vimeo embeds, etc.) so I figured I would keep this site "current" on my own.
I didn't want to work in PHP though, so tonight I wrote a gelato clone in Rails. It's a bit of a mess still and I haven't ported over every single feature (such as the commenting, which was only picked up by spammers anyway) but for now the basic functionality is here. I've kept this same crazy theme though i think I'm going to overhaul it at some point, and there will be other things I add as my time allows.