For those that don't have a .edu address, Office 365 is available on subscription, $10 a month and they give you 5 licenses you can put the software on a PC or Mac in any combination.
Businesses can subscribe for $15 and you always have the latest update. One cool feature if you have the 5 comps maxed out, is you can decommission a computer without removing the software and use a 6th computer. So in theory if you move around a lot you could have office on any number of computers. But no more than 5 per license at any one time.
A great deal if you ask me.