XKeyCaps
A graphical front-end to xmodmap. It opens a window that looks like a keyboard; moving the mouse over a key shows what KeySyms and Modifier bits that key generates. Clicking on a key simulates KeyPress/KeyRelease events on the window of choice.

WMKeyboard
A WindowMaker dockapp that allows users create and apply keyboard maps. It also acts as a switch between two keyboard maps of choice.

Swapping [Delete] and [PageUp]
This page describes how to swap keys under Linux, X, bash, and tcsh, using the misplaced keys of the Logitech NewTouch keyboard as an example.

The Linux keyboard and console HOWTO
The LDP keyboard and console HOWTO.

Keyboard mappings (Backspace & Delete)
For Linux Laptop at Linux Tips and Tricks.