At http://shop.oreilly.com/product/0790145305770.do?code=MSDEAL, Microsoft Press are offering the Microsoft® Manual of Style, 4th Edition as a PDF for 50% off using the MSDEAL code.

"Maximize the impact and precision of your message! Now in its fourth edition, the Microsoft Manual of Style provides essential guidance to content creators, journalists, technical writers, editors, and everyone else who writes about computer technology. Direct from the Editorial Style Board at Microsoft—you get a comprehensive glossary of both general technology terms and those specific to Microsoft; clear, concise usage and style guidelines with helpful examples and alternatives; guidance on grammar, tone, and voice; and best practices for writing content for the web, optimizing for accessibility, and communicating to a worldwide audience. Fully updated and optimized for ease of use, the Microsoft Manual of Style is designed to help you communicate clearly, consistently, and accurately about technical topics—across a range of audiences and media."



There is a sample chapter for free download at the above link