In response to a comment from M. at the Pappmaskin Diaré Techblog, a quick review of how the categories / tags thing that I'm peddling works:
All of the del.icio.us tag generators that I refer to in my posts include the rel="tag" attribute, and are therefore detectable by t'rati and other tag search engines. Since del.icio.us requires that you bookmark stuff there by hand, you'll still need to do that, & I think the extra visibility of your material on del.icio.us makes it worthwhile. Think of del.icio.us as your category manager, with the added benefit that some other people will see your stuff there. Think of t'rati & the other tag engines as icing on the cake.... a powerful side-benefit of this system that increases the visibility of your material even further.
Now traffic won't translate to inlinks & ranking, of course, but if the original material is good enough, this seems like a pretty good strategy for getting it seen...
& to address the comment specifically, you can still link to a technorati search (either for cosmos or keyword, I guess) from your post footer if you want to... This isn't an either / or proposition.
See also PDT's other idea for faking out categories. I won't pretend to understand it. Too many onion layers. I'll wait for the "this idea for dummies"... ;-)