Importing custom databases into Drupal.
I have in front of me a fairly complicated db structure from a custom CMS that I've been charged to import into Drupal. I'm just getting started with Drupal's node structure, so I'm a bit worried how I'm going to be able to retain the content heirarchy and also preserve the cross reference tables (for example, vendors can belong to multiple categories and categories have multiple vendors, so a cross reference table is used to map the many to many relationship). I'm pretty familiar with how to do this if I'm writing code from scratch - but at a bit of a loss to do it with Drupal
Anyone recommend any tutorials out there on doing this sort of thing? I'm going through the Google hits I've found for this, but the articles its pulling are uneven. The Feeds module keeps getting mentioned, but since I'm reading in a database (or more accurately a set of CSV files I've converted back into a database in order to analyze their contents) it isn't going to be much use.