Visual Bindings is an on-screen full layout keyboard, with buttons for every key found on a standard keyboard. When mousing over a key, a tooltip frame pops up showing any action bound to that key, or any combination of modifiers plus the key.

Example: Mousing over "F1" on my druid shows:
Binds for F1:
F1 TARGETSELF
Ctrl-F1 SHAPESHIFTBUTTON1
Shift-F1 TARGETPET


Most keybinding addons allow for easy binding of the keys, but I've yet to find one that intuitively shows the bindings already set for each key. This is my attempt to make it easier to know what actions are bound to each key.