Most of the following rather for the interested than as a fast help.
If you want to map western european 8bit characters, you need their KeySym-names:
You might as well be interested in Jörg Knappen's postscript file "charset Latin-1 and the character names under LaTeX, HTML, X11 (xmodmap) and PostScript"
If you want to use such characters in your applications, you might have to take care of your locale settings, as Unix originally is rather 7bit (ASCII) by default.