What are these things hanging off the trailing edge of the wing? What are these things hanging off the trailing edge of the wing?

I've seen them in almost all of the aircraft I've flown in, and can't remember if they're exclusively Boeing or Airbus.
Those are static wicks -- Basically these are little wires screwed to the airframe.
Their purpose is to discharge the static electricity that an aircraft picks up moving through the air - especially in clouds.

The static discharge tends to happen at "pointy" protrusions from the aircraft - if this happened through antennas it could cause radio and navigation interference, so to prevent that static wicks are installed, providing a low-resistance protrusion for the charge to dissipate through (and as an additional benefit, dissipating the charge helps ensure your aircraft doesn't attract lightning strikes).

Here's a couple of closer pictures: