These days the Office Suite programs that contain word processor, spreadsheet, etc. gets larger and larger each year. The lastest Microsoft Office 2010 needs at least 3GB of disk space. Even the Open Source Open Office needs at least 650MB of disk space. These might be able to fit into a USB thumbdrive, but a better way to have a portable office suite such as the OpenOffice Portable. It contains a web browser, email client, office suite, calendar, instant message, and backup program all that be run from a USB drive.
Some of the advantages of having a portable office suite are the ability to run a suite of programs without first installing them and being able to take them where ever you go.