Microsoft Office Professional Plus 2013 - $15 (select email accounts)
Office Professional Plus 2013 Product Key $15
Visio 2013 $15
The Home Use Program is a Software Assurance benefit available to Microsoft volume licensing customers with active Software Assurance coverage on their Office applications. Employees who use the covered licenses at work are eligible to purchase these Office applications for use on a home PC during the term of their employment. This temporary license expires with the employers Software Assurance coverage, or upon termination of employment with the covered customer.
MS Office is available in Mac and Windows 32-bit and 64-bit versions, but the recommendation is that most users are better off with the 32-bit version even if they have a 64-bit version of Windows, largely because it provides better compatibility with older add-ins for Office.
It's a hefty download at 667MB for the 32-bit version and more for the 64-bit version.
You'll need Windows 7 or 8, or Windows Server 2008 R2 or 2012. Office 2013 won't run on Windows XP or Vista. There are various other requirements, so it's wise to check the small print before downloading, but most PCs purchased in the last few years should be OK.
One Note 2013
Info Path 2013
Excludes Visio 2013 but you can buy for $15.
Note: This version uses "Click-to-Run" it doesn't download the full install program (as it wants to install to your pc). Click-to-Run is a new way to download and install Microsoft Office. With Click-to-Run you can use your Office programs as they are streamed and cached on your computer. You can also install the program using your product key with the Microsoft Office Professional Plus DVD $15 or install image (available elsewhere).
A 60 day trial version is available from http://technet.microsoft.com/en-US/evalcenter/jj192782.aspx