Free resources from "Sharpening Your Writing Skills" by Duncan Kent & Associates Ltd. at
http://www.techcommunicators.com/publications/sharp.htmlChapter 1. Good Business Writing Style
Chapter 2. Planning to Write
Chapter 3. Writing Strategies
Chapter 4. Words and Sentences
Chapter 5. 20 Rules of Plain English
Chapter 6. Punctuation Matters
Chapter 7. Designing Effective Pages
App 1. Answers to Exercises
App 2. Writing Styleguide
App 3. Dictionary of Plain English
Note: Complete PDF available for download.