Microsoft has great social media policies for their employees and product groups. Most of the Microsoft products have their own Twitter account posting news and information about it. In fact, there are hundreds of official Microsoft Twitter accounts right now.
Microsoft has now created the most up to date and comprehensive reference of active Microsoft Twitter Accounts on TechNet Wiki. Right now, this list has a categorized listing of 215 Microsoft Twitter Accounts representing official Microsoft products, teams, projects and initiatives along with widely recognized influential personal Twitter Accounts of individuals who work at Microsoft.
The TechNet Wiki truly is a place where collaboration happens. This article is managed and maintained by the TechNet Wiki Community and is the result of efforts by community members at large, the TechNet Wiki Community Council and from contacts at Microsoft. A big thank you to everyone who contributed!
You can check out the list here.
Source: Official Blog of TechNet Wiki