Completing our overhaul of the taxonomy system (including categories and tags), you can now do everything you used to do with categories and tags with any taxonomy. While this may seem like a small change, it's a big shift in how you can organize more complex databases. Here's a couple of articles that explain it in detail:
Taxonomies Grow Up explains what has changed, and why
Working With Taxonomies gives all the details of how to access taxonomies with WebvantaScript.