Microsoft announces expanded BPOS-Standard support for the Mac OS with the introduction of a new Microsoft Online Services Sign In application that supports the recently released Office for Mac 2011. The new Sign In application for Mac OS is scheduled to be available by the end of March 2011. In addition to support for Office for Mac 2011, the new Sign In application includes a number of bug fixes and enhancements that improve the performance and stability of the application for the Mac OS.

http://blogs.technet.com/b/msonline/archive/2011/03/02/new-sign-in-application-supports-office-for-mac-2011.aspx