A while back our internal web host went down (which in turn hosts a staff/student internal homepage) - we've got it setup so that on loading IE or clicking home you get that intranet page AND the schools main website (in a second tab).
With the server down the intranet didn't load but the school website was up and running fine - would be amazed at how many calls we got asking if the internet was down only for us to respond with no its just the intranet.

