… or "how I re-invented the wheel". Again
I found myself needing a tertiary menu in Drupal yesterday, which sadly it doesn't provide by default. There is a primary menu and a secondary menu that can auto-populate based on the primary menu selection, but sadly that's the level at which it stops.
Google helped me find a few blogs that show how to easily generate an arbitrary level sub-menu, though most are for D5 and not D6. Ignacio Segura amended code on this blog that makes it all work for D6: