There is only one Microsoft Office… there are alternatives but so far nothing has eclipsed Microsoft in this field.
Today Microsoft Released Office 2011 for Mac. It replaces Microsoft’s Mac-specific Entourage email app with the industry standard Outlook, brings in some interface tweaks from Office 2010 over in PC land, and integrates with those Office Web Apps you’ve been hearing so much about.
“Office 2011 has new built-in integration to existing Microsoft cloud-based applications—the free Windows Live SkyDrive, Microsoft SharePoint, and Microsoft Office Web Apps,” Eric Wilfrid, Office for Mac’s general manager, wrote in an Oct. 26 posting on the Office for Mac blog, “giving users more flexibility and control to work when and where they want.”
More information can be found here.