OpenOffice -- http://www.openoffice.org/
If you haven't heard of OpenOffice yet, you're probably not a techie....and that's ok!
If you use Microsoft Office for the basics (simple word processing and spreadsheets), you should feel completely comfortable working within OpenOffice. It's a free office suite, and works very similar to Microsoft Office, and even better is that you can OPEN and SAVE documents in the Microsoft Office format. Plus, you can easily create PDF documents right from OpenOffice without the need to have any special PDF-creating software on your computer.
There's absolutely NO REASON not to try (and hopefully switch over to) OpenOffice if you're a standard/basic MS-Office user. If you have custom macros, however, they may not work in OpenOffice the same, so heads up on that.
