Put top categories on subdomains

Hi,
I’m in process of restructuring my blog. I would like to separate the main blog categories (web, mac, personal) onto sub domains (i can set up wildcard dns) and there they will have more sub categories and slightly different design (perhaps different header image and color scheme.
Basically, something like slashdot.
The reason I don’t want to use MU is that I’m the only author, and I don’t want to have to log in to multiple blogs.
here is my blog if anyone has any suggestions. thanks!