The latest version of the SDK for Dynamics CRM 2011 was released yesterday night.
This version is for CRM 2011 On Premise and for some time for the online organizations that have not yet been updated:
http://www.microsoft.com/en-us/download/details.aspx?id=24004
The list of changes can be found on the following site:
http://msdn.microsoft.com/en-us/library/dn457782.aspx
For the CRM Dynamics 2013 SDK you can use the following link:
http://www.microsoft.com/en-us/download/details.aspx?id=40321
Cheers,
Mario