Microsoft updated their Mac Office 2011 page today on multiple editing with Sharepoint/Skydrive.
Collaborating with friends, colleagues and classmates is worry-free with the co-authoring tools in Office 2011. Documents can be stored in the cloud (SkyDrive free to consumers and SharePoint for businesses) allowing for multiple people to access and edit a document. In addition, there is built-in support for the Office Web Apps. That lets a user edit an Office document, even if they are at a machine that doesn’t have Office installed on it.
The team also announced new features in Outlook for Mac including the scheduling assistant, which allows users to see their calendar in line with their mail resulting in a more efficient workflow. Additionally, PowerPoint 2011 allows users to broadcast a presentation. Broadcast Slideshow lets the users of your choice view your presentation at your speed, all recipients need is a browser connection.