Mr. Obama is doing a really nice job of revamping the US nuclear arsenal.
He is planning a new series of weapons that will be called
Interoperable Warheads (so named because they can function on either an ICBM or SLBM without modification).
IW-1 will have a yield of 455 kilotons. It will be based on the W78 used in the 3-warhead MIRV from the Minuteman 3, but with an upgraded secondary for a higher yield. The UK plans to deploy the IW-1 on their SLBMs as well.
IW-2 will also have a yield of 455 kilotons. It will be based on the W87-1 that was designed for the canceled midgetman road-mobile ICBM. This will provide the US with two independent designs for a half-megaton ballistic warhead.
IW-3 will have a yield of 100 kilotons, and will be based on the W76 warhead currently used on many of our SLBMs. Clearly not as much punch as the other two designs, but a good fallback if we should happen to have a critical flaw in both of the larger designs.
Mr. Obama is also planning to bring a "usable" tactical nuke back to European soil for the first time since the end of the Cold War:
http://fas.org/blogs/security/2014/01/b61capability/
http://fas.org/blogs/security/2014/02/b61-12pictures/
http://fas.org/blogs/security/2014/03/b61-12integration/
http://fas.org/blogs/security/2014/04/b61-12features/