With Interception you are able to intercept and transform input data from keyboard and mouse. Support is still Windows only (from Windows XP to Windows 10).
See also https://github.com/oblitum/Interception
Keytweak is a free keyboard remapper for Windows NT/2000/XP. It makes use of Microsoft's Scancode Map registry key to remap your keyboard. VB6 Runtime files are required, but are already present on Windows 2000/XP.
Description of Conkeror, an extension for Firefox which allows controlling the browser with (mostly Emacs-like) keys instead of mouse clicks.
On 2021-10-12, the site was off-line and the http://conkeror.org extension is probably obsolete.