My GNOME keyboard settings do two main things:
- Switch CMD and CTRL (I'm on a Macbook)
- Give me a third level (for special characters)
This is really the only functionality I'm missing in Fluxbox. Any way to activate it without running GNOME?
If, by "third level", you mean using eg. the American Internation keyboard layout, you can set up your system to use it by default.
There's probably a lot of other places for keyboard configuration on other flavours of Linux – on Gentoo/Funtoo it's in
Regarding switching the CMD and CTRL keys, I think it's already been answered here: Map "windows" key on keyboard to "ctrl".