How can I access an external table in a MySQL database?
Here is a module that will help you: http://drupal.org/project/data

[ edit re MPD suggestion below ...]

This module will help by providing an automatic Views integration for your data, meaning that you can show the data via Views.

It also includes an API which simplifies custom programming to get access to your data (perhaps for use in preprocess functions, which would permit the data to be themed on a node page, etc.)

Regarding your desire to include taxonomy, one way to do that would be to fold the data onto a node and then attach taxonomy to that node, however, that might depend on how you're mapping your data onto individual nodes.