easily/safely type unicode characters?

[Carlo Nyto]

I have the occasional need to type unicode characters. It is rare
enough that I don't want to change my keyboard to a foreign mapping
and deal with the strange (and dangerous on the command-line)
side-effects.  But it is often enough that the character map is a pain
to use. (although it has been a lifesaver, as I can find no other
reiable solution)

What is my best solution for a way to enter those characters needed to
spell correctly in German and Spanish using only the keyboard, but
without using keyboard settings that produce surprising results? Of
course I want it to be the same across all applications, be it vim in
an xterm, gnome-terminal, konsole, a text editor window in firefox, a
gaim window, openoffice. If it's not the same across applications it
just leads to frustration and mis-typing. As a native English speaker
who uses the command line heavily, I don't want to do anything that
makes it more difficult to type in English, nor that leads to
dangerous command-line behavior because of unexpected character
sequences turning into something different.

I'd rather not memorize every unicode character number and use the
ill-documented ctrl-alt-XXXX syntax (which I can't make work under any
application in ubuntu, nor can I find any documentation pertaining to
how this syntax actually works. I can't even find documentation
explaining whether I should enter the characters in hex, decimal, and
if decimal whether the numeric keypad must be used).

I appreciate any help along these lines. I can't be the only person
who uses ubuntu primarily for English with a US keyboard, but wants to
be able to type foreign words naturally and without causing strange
interactions because of unnecessary overloading of commonly used keys.
I also can't be the only person who wants the same keyboard sequence
to produce the same characters in every application.