Office 2011 for Mac OS X is currently in the beta testing phase. Microsoft has sent beta invites for the build number 100709.
The email states, "The Office for Mac 2011 beta is closed to the public, which means ALL Office 2011 tools and features are confidential and proprietary to Microsoft. By participating in the beta, you consent to a non-disclosure agreement which includes all forms of communication including print, broadcast, electronic, Internet publications, social media networking sites, blogs, and verbal disclosure. The NDA will not lift until the product is public later this year. We will update on timing closer to the date."
Microsoft officials say Office 2011 for Mac will be available this holiday season