Scott,
For this iteration it is a semi-custom, semi-hacked, semi-kludged, wordpress theme with very very few plug-ins. I run it on a very very cheap piece of my server cloud. The image icons etc are a real pain to manage and I just type directly into the wordpress web interface.
Honestly I am really digging posterous.com and would probably go that way if I had the time to move my content and make it reasonably accessible. Either that or a custom content engine built by me in ruby. I am not a big fan of the wordpress creeping horror at this point but I have a 3 or so year investment in content. Maybe I will move it all to posterous.com on a weekend that I am having some sort of drinking binge and see how it goes...
If you are looking for a really cool blogging platform check out posterous
RB