The series plugin does sound like a good idea for organising old posts. I’m currently a bit dissatisfied with my navigation set-up: I just changed all my categories to tags because I was effectively using them that way – as keywords, that is – and in WP 2.5 having a lot of categories completely slowed down some of the admin pages, and I was finding it so irritating. Supposedly 2.5.1 has improved that situation, but I can’t change back now…
What I really want is something with just a bit more organisation than tags as they usually are: as it is I have a tag cloud with all 571 tags all mixed together, which isn’t very user-friendly. My ideal would be several tag clouds divided into broad categories like ‘art’ and ‘books’: if you’ve seen tag-bundling on delicious, that’s what I have in mind. A kind of very shallow hierarchy. Or, if I’m inventing solutions, a single dynamically generated tag cloud that displays some chosen subset of the total.
I don’t actually think that anyone uses my archive pages much, so I’m not going to lose sleep over it. It just annoys me when I don’t think something is quite working.
I think the sidebar list of favourite posts is a good idea: the only thing I sometimes miss about not having a proper sidebar is some way of pointing readers back to selected material from the archive. Just having recent comments displayed made people much more likely to click through and see what was being said.