I've just installed Ubuntu Server 11.10 and the tilde (~) and double quotes (") keys don't do anything - they don't print to the screen. I'm only using the command line (no GUI) and many tutorials say to use setxkbmap and xmodmap which aren't working for me.
For those not using XWindows, e.g. Ubuntu server,
setxkbmap won't work.
sudo apt-get install console-common
Or if it is already installed:
sudo dpkg-reconfigure console-data
Follow the instructions to set the keyboard, e.g. for me, "pc / qwerty / US american / Standard / Standard".
You can change the keyboard in the Ubuntu System Settings, Text Entry. Remove the English(UK) from 'Input sources to use:' by selecting it in the list and clicking '-'. (Tested in ubuntu 14.04)