Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I am a Linux user, and I recently got an eMachines laptop. Since I'm Uruguayan, my mother tongue is Spanish, and that presented a problem: laptops usually have an American-style keyboard, and Spanish (as well as Portuguese, French, German, and other languages) requires some special keys that aren't on American keyboards. Here's how you can get international characters on your American keyboard -- and as a bonus, we'll see how you can enable the special "media" or "Internet" keys on some keyboards that aren't supported by Linux out of the box.
When you set up Linux (I'm using openSUSE 10.2) the keyboard on most laptops is detected as "Generic 104 key PC" (or 102, or a similar number; check your laptop) with a "US English" layout. In such a keyboard, you won't have any special keys for letters such as "Ñ" or "Ç," and you also won't be able to use tildes to get "ã" or "ü." (And, by the way, the Windows ALT+nnn combinations won't work, so don't even bother.) However, you can work around this by "composing" the desired characters by pressing a pair of keys.
If you are feeling adventurous (or you don't use openSUSE) you can edit the /etc/X11/xorg.conf file directly with any text editor. Look for the "InputDevice" section that deals with the keyboard, change it to look like the section below -- note the XkbVariant line -- and the next time you start a GUI session, the keyboard will be OK.