If you're asking this because you're looking for a working dog that will guard your sheep/goats/chickens/etc, most livestock guardians are suited to being outside.
However, if you're asking this because you would simply like an outdoor pet, livestock guardians are not for you. Without a job to do other than be a lawn ornament, they WILL become unsociable, miserable dogs. You do not want an ill-mannered 100lb dog. Trust me on this one.
http://en.wikipedia.org/wiki/Livestock_guardian_dog
http://www.lgd.org/
http://www.canismajor.com/dog/livestck.html
