Free Office Suites
Compatible with Microsoft Office
GoogleDocs online
Google Cloud Connect for Microsoft Office (Convert Microsoft Docs to Google Docs)
LibreOffice client software
OpenOffice client software
Microsoft Office Suites
FREE
Ask your teacher, school IT lab or student bookstore how to obtain the free Microsoft MSDN Academic Alliance version of the software.
http://msdn.microsoft.com/en-us/academic/default.aspx
If you can download the iso image, here's a good free iso burner in case you need one.
http://download.cnet.com/Active-ISO-Burner/3000-2646_4-10602452.html
DISCOUNTED
Check your college book store for the Student edition of Microsoft software, or buy online here.
http://www.journeyed.com/select
Office Student Edition.
http://www.microsoft.com/student/en/us/office/default.aspx
Online
Office365
http://www.microsoft.com/en-us/office365/hosted-solutions.aspx#fbid=khugsF8SHts
Office Web Apps
http://office.microsoft.com/en-us/web-apps
If you are not a student and want to pay less than retail you can find Microsoft software on eBay.