This guy uses Moveable Type, and has a secondary blog called “Neil’s Smaller World” embedded into his primary blog, in the sidebar. This is similar to what Luke does.
I’m not sure if I could get WordPress to do that or not. I know that WordPress doesn’t support multiple blogs with one install, so I would have to install WordPress into the main journal directory and into the sidebar directory. Then it would be a matter of a php include, I think.
It seems doable. I just need to figure out if everything would render correctly.