During the heroic, night-time raid on Osama's compound, some sort of malfunction or incident forced the infiltration team to scuttle one of the helicopters used on the mission. The tail section apparently fell outside the compound on the other side of the 12 foot walls and was left behind, relatively intact. The initial photos are intriguing and will no doubt lead to much speculation on the type of helicopter it was; a new type or a heavily modified H-60 type.
No doubt foreign intelligence agencies (I'm looking in your direction, China) are en route to the Abbottabad area to attempt to secure those fragments like they did to downed F-117's in former Yugoslavia.
I don't think this is a modified H-60, as the tail rotor is on th eopposite side of the tail, which would be a considerable engineering rework. What I can't tell is if the tail elevator is canted to the front or back of the tail.
More pictures will be added as I find them.
More information at Aviation Week and DefenseTech.org.
[update] Probably an MH-60 varient: armytimes.com
This also looks pretty compelling: