If you don't have the latest spreadsheet or word processing software don't worry.
Google Pack is a collection of pwerful, easy to use software available directly from Google.
There are no trial versions or spyware, and the whole pack is ready to use. You simply select the software you need.
If you need more information on what's available have a look at Free Google Pack Blog This is a blog entirely dedicated to the Google Pack. This goes into a lot more detail so it's well worth a look.