OpenOffice Portable – Free Office Suite
OpenOffice Portable: OpenOffice is an Open Source Office Package, a Free "Portable Office" software created by OpenOffice.org and packaged with a portable wrapper by Portableapps. It ships with a word processor, spreadsheet software, presentation software, drawing utility and a database. OpenOffice is compatible with Microsoft Office and other office suites and can perform all of the major functions you come to expect from a good office package.
OpenOffice Portable Screenshot

Extracted Size: 240MB
OpenOffice Website: OpenOffice.org
Open Office Portable Page: OpenOffice Portable
License: Open Source
Download: Get OpenOffice Portable HERE
Note: OpenOffice Portable is a large package and will take some time to extract to your USB device.