Welcome to the Seven Forums! finchtosh
The only edition seeing a "Family Pack" unfortunately is the Home Premium edition allowing upto 3 machines per family household. In fact newegg one vendor originally had some specials going with those when 7 was first released last fall.
MS used to have small business licensing available for upto 15 systems for that type of volume license to serve small business interests you had to buy separately. Haven't heard anything more on that for 7 however.
Your alternative of course for using the same disk on any other machine would simply be buying a new license for each.