So you or a team member has a Mac and is using the Lync for Mac client and now they want to explore their sharing options. Start with the feature comparison chart here: http://technet.microsoft.com/en-us/library/gg425836.aspx
You will notice they can’t present a PowerPoint but turns out there is a workaround, and like all workarounds isn’t perfect for everyone. If a Windows Lync client is joined to the meeting they can upload the PowerPoint presentation and then the Lync for Mac user can take over the presenting.
Hopefully this is one small workaround that helps you (thanks to our test team for mentioning this).