Is there any STANDARD U.S.-compatible keyboard layout for typing extended Latin?

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http://superuser.com – I am getting REALLY tired of adjusting my typing habit when needing to type characters such as ø, å and æ to name a few, after switching from Mac OSX to Windows to Mac OSX, which I unfortunately have to. Haven't tried Linux recently, but it could prove to have its own layout again. Is there any standard layout one can expect? To type ø for instance, I need to hold down Alt key and hit the O key on Mac. Simple enough. On Windows however, that would be Alt and L. Is there any standard layout for my usage pattern? I am typing mostly Norwegian, but occasionally also Swedish letters. If I k (HowTos)