I am guessing by now everyone that follows Twitter should have seen the flood of tweets around this but I thought I would put together a couple of important links if you didn’t.
Official Provisioning Guide:
For some companies already federated with MSN you may only need to edit your current PIC provider where as others that have never enabled PIC will need to go through the whole PIC enablement process.
From the configuration guide:
To edit a Messenger PIC provider and configure it for Skype, do the following:
1. From a Lync Server Front End Server, open the Lync Server Management Shell.
2. Run the following two commands:
Remove-CsPublicProvider -Identity Messenger
New-CsPublicProvider -Identity Skype -ProxyFqdn federation.messenger.msn.com -IconUrl "https://images.edge.messenger.live.com/Messenger_16x16.png" -VerificationLevel 2 -Enabled 1
3. From a Lync client, you can now select Skype as the PIC provider, and add a Skype client by specifying their MSA account. .