There are some free alternatives out there. The two I use are Google Docs and Openoffice.org.
Google Docs, detailed more here, is great for online collaboration of documents because you can share the documents with others. Everything is hosted online, although there is an offline version. It is great for students because their documents are stored online and they can access them from any internet accessable computer. Google Docs includes word processing, spreadsheets, and presentation applications. Because it is web based, you can use it on Windows, Mac, or Linu. And, it's free.
Openoffice.org is free software from Sun Microsystems. Unlike Google Docs, Openoffice is software you download to your computer and the files reside on your computer. (for ideas on syncing files among multiple computers, check out SugarSync).
Openoffice is a fully functional office productivity system that rivals Microsoft Office in many ways and includes applications for word processing, spreadsheets, presentations, databases, formulas and graphics. I have found it really easy to use coming from Microsoft Office since the menu's and commands are very similar. Openoffice can save files in many formats, including Microsoft Office formats so that you can use them on other computers without a problem. Openoffice is available in multiple languages and for Windows, Mac, and Linux.
Google Docs and OpenOffice can save students, faculty, and schools a fortune in licensing fees and allow better collaboration and productivity.