The one thing that most of us Linux users miss when leaving Windows behind is that «alt codes» are not supported. Well here is an under documented feature that should allow you to type alt codes and access all of the special characters with Ubuntu, Red Hat or whatever flavour of Linux you play or work with.
Windows «Alt Codes» for Linux works like this.
Ctrl+Shift+u
Hold down Control and then Shift and press the «u» key. You should get an odd looking character that is waiting for input. Type the numeric code and press space. You can use more than just ASCII but can use hex values too!
Now you can type and unicode value and get the character in you Linux text field. Feel free to say how fantastic I am.
So now you can type your «æ» or «Þ» or whatever. Spend only ¼ of the time typing characters and more time being cool.
Need a better look up for characters? http://unicode.org/charts/ is a full collection of PDF charts of all the information you should ever need.
ps. This took word-by-word from here: Use Windows «alt codes» in Linux but better, by Lord Matt.