These tools can be used to transform a file or group of files from one format (e.g MS Word) to another (e.g. PDF).  It would be impossible to provide a complete set of such tools, but some other common applications for file transformation are discussed at:

article listing file conversion tools

The rest of this page lists some free and or low cost tools

Multitype

• Xena
• Zamzar

Documents/Text/Spreadsheets

• ABC Amber Text Converter
• Cogniview.com list of free PDF ultilities
• Excel to PDF
• PDF Creator

Email

Resources regarding email conversion at eMailMan.com

• CERP Email Parser (small talk, runs in squeak VM)
• Aid4Mail
• EMCAP

Images

• GIMP
• Image Converter .EXE
• ImageMagic

Audio/Video

• Audacity
• Mediacoder