@MSExcel - Official Twitter account of the product team that brings to you a little piece of software we call Excel.
@msaccess - I am Ryan McMinn a Program Manager on the Access Team; email me at firstname.lastname@example.org
@Office - Tweets to help you do more with Office at work, home and school.
@OfficeBI - Covering Microsoft's Business Intelligence products on the Office Platform including SharePoint, Excel, & Excel Services.
@Office_Live - Tweets from the team at Microsoft Office Live
@SharePoint - The SharePoint Product Group
@ch9 - Channel 9 keeps you up to date with videos from people behind the scenes building products at Microsoft.