I am a little behind the curve on this, but in the most recent update to Mac Office Communicator, Microsoft has added Desktop Sharing for the mac clients. This is one of the last features that was in the Lync client that was still missing from Communicator for Mac.
For all the info on the update go here. To update the clients kick off Microsoft Office Auto Update and it will download the new link client.
The one one remaining feature missing… white boarding and PowerPoint sharing…. but I can live without that for now.