The forthcoming 0+5i release of Blosxom enables you, the blogger, to define your own output flavours (read: templates, although I've never much cared for the word) beyond the default HTML and RSS output formats -- and it goes without saying that you can change those two too.
For example, take a peek at an outline view of my weblog. I'm making use of Marc Barrot's excellent Javascript
outliner functions, as featured on his weblog, slam".