I see book authors, editors, bloggers, press, team members, and occasionally even a VP misspell our products, technologies, and features that I thought I would build and maintain a list of the correct capitalization and spelling of the most commonly misspelled Microsoft products and technologies.
Sources: Internal site (brandtools) and the Microsoft Trademarks Web site.
I was gently reminded today (Thanks Brian) that it's .NET, not .Net. I always seem to screw that up. Luckily Brain also directed me to this post by Dan that makes it so easy that even I can use it. (Damn, does that mean I don't have any more excuses? grrrr... ;)