Note this reference is not exhaustive and mainly details
useful and non obvious default keyboard shortcuts (bindings).

help apps (presented first since there's a bit of a catch 22 in regard to them :-))
    info
    less (used to view man pages)

terminals
    Linux virtual consoles
        X
            windowmanagers
                windowmaker
                sawfish (like windowmaker and can be made the same easily)
                metacity
                kwm
            gnome2
                metacity (windows key bindings)
                gtk2
                    GtkCList
                        Multiple selection mode
                gnome-terminal
                nautilus
            kde
                kwm
            Apps
                nedit
                mozilla/galeon/firefox
                xchat
                Gimp
                xine
    readline (bash/python/ftp/bc/gnuplot/...)
    bash
    ssh
    telnet
    top
    vim
    mc
    screen

Note the Linux Keyboard and Console HOWTO has some very good info.
You may also want to compare the other side's documentation.