What is this unusual leading edge flap on a B737-200?
These are two leading edge Krueger flap surfaces at each side of the wing, you can see details about them according IPC and AMM documents I found over the internet:







Regarding the Addendum, and why it seems that there is no other flaps deployed, I found a similar topic at Airliner.net Forum. As it is mentioned there, when is no hydraulic pressure, they can be extended by their weight:


  ...it has to do with the shut off valves and the actuators relaxing with no hydraulic pressure on them.


and also:


  ...Pressurize the system and they all move to their present commanded position


and another sidenote:


  ...Someone pulled that Krueger Flap to the fully extended position. When they droop because of no pressure on the system there in the mid positions. 


and as final note, this issue is also mentioned in the AMM: