I have been using Libre Office instead of Open Office for a few installations now and I want us to standardise on this as our recommended free alternative to MS Office.
Couple of advantages I am aware of:
1) reads old MS Works files (yes some customers do still have these!)
2) can save in MS Office XML formats (.docx, .xlsx etc).
Download Windows and Mac versions on to your portable media so you have them handy.
When you install it please make sure of a couple of things:
1) Set the default file saving formats to MS Office files - go into Preferences (Mac) I think its Options in Windows and set up the default File Formats for Text, Spreadsheet and Presentation as XML. Uncheck the Warn box!
2) make sure Libre Office is the default program for appropriate file types - Control Panel, Default Programs in Windows, use one of these methods for OS X if it has not already set the default (test it first!)