This is a good basic overview, goes beyond tagging/indexing, was the textbook in LIS501 Information Organization and Access at UIUC-GSLIS (now the iSchool at Illinois) in 2006:
I could, but honestly I'd just be googling "taxonomy". But ok that's not entirely true, I know how to refine my search and recognize when something is what I'm thinking of, from some familiarity with the field.
(But if you want to look around, in addition to "taxonomy" and "ontology", other good terms are "information architecture" and "controlled vocabulary").
These are not things I have vetted, this is literally just me googling and taking a quick skim...
