The Compose Key in Xorg
I wanted to enter in some characters that were not on my keyboard. To do this, I enabled the compose key. This lets me hit a combination of keys to form a single character. For example, + <"> + = ä, + + = ©, and + + = ¿. There is a short list at the wikipedia article on the Compose key. The wikipedia article also has a link to the longer list. I believe you can create custom Compose key combinations by using an ~/.XCompose file, but I haven't tried this yet.
I mapped the compose key to the menu button (the one next to control and windows key on the right-hand side of my keyboard) with: xmodmap -e "keysym Menu = Multi_key". This only changes the key mapping for this session, to make it permanent: echo keysym Menu = Multi_key >>~/.Xmodmap
I mapped the compose key to the menu button (the one next to control and windows key on the right-hand side of my keyboard) with: xmodmap -e "keysym Menu = Multi_key". This only changes the key mapping for this session, to make it permanent: echo keysym Menu = Multi_key >>~/.Xmodmap