Deleting non-music files from an iPod

I seem to remember being able to do this on my old iPod but can’t see how to do it on the new one. I want to get rid of the files for things like non-English languages that I don’t need. IIRC on the old one the files were visible on the iPod itself but here they’re all invisible. Other than doing a custom install which is more trouble than it’s worth, any suggestions?

It’s a 20 gB running 3.0.1 and I use a Mac, if any of that makes any difference.

No one?