Categories and indexing

Hi. I came across del.icio.us in an Infoworld article, and figured: What if we make an RFC for categories. If we had a set of standardized categories people could choose to use, we could have blog indexes where we could subscribe on a category in a language as an rss feed and receive only interesting topics on that. An example of a category could be Music/Early Music/Renaissance, as opposed to Art/Renaissance/Vermeer. I'd love to receive blogging on Vermeer and Renaissance music without having to hunt these blogs down and add them to my RSS feed.