I'd like to show peripheral categories when viewing an archive page of a category.
Say I'm on archive for category "car". I would like to show a list of all the categories that these posts contain. This could be "wheel", "color", "motor". If I have this list I would like to refine my selection using boolean AND.
This way I would be able so see all the "car" posts that also share the "motor" category.
I noticed that I can use /?cat=2&cat=5 in the URL to show posts that share both categories. But I don't yet know how to create the list of peripheral categories, and how to build the link.
By the way, you can see this method of refinement on del.icio.us. It's called related tags, and by hitting the "+", you can refine your selection very easily ...
Thanks for any help!