Microsoft took the wraps off of Windows Phone 7 series for mobile and said it will start appearing on devices by holiday 2010.  The company highlighted features for the new operating system including integration of Xbox Live, Zune and Bing into the software.  Microsoft outlined Windows Phone 7 features as falling into six categories, listing them as People, Pictures, Games, Music + Video, Marketplace and Office.  The Games category will offer what the company calls an official Xbox Live experience, including merging user data from Xbox 360 and offering Xbox Live games.  The Music + Video category gets Zune branding, while Marketplace acts as a separate category for accessing third-party apps and content.  Microsoft said every Windows Phone 7 series device will also have a fixed button linking to its Bing online search engine.  Read more in the company press release.