I have installed SharePoint SP1 on my development machine. Yammer and OneDrive links have appeared in the Central Administration:
If you go ahead and click “Configure Yammer”, you can activate it:
Yammer is Microsoft’s recommended tool for social collaboration.
When you activate Yammer, you’ll get this dialog, and the Yammer link in the SuiteBar:
What happens when you click on Yammer, is that you are redirected to Yammer.com and you are prompted a login page.
Then you have a usual yammer site with all your networks and stuff (in my case, SPC14 network):
Then, if you go to your newsfeed, the following message is shown:
This page displays updates for sites you’re following. To connect with people, use Yammer.
There are still many questions about the Yammer and Newsfeed. But I like the activation process in the SharePoint 2013 SP1