Lizard Skins Headset SealMade from neoprene. This cover wraps around your headset giving you protection from dirt, water and grime.
But then again, I think I have an internal or integrated headset that doesn't get nearly the exposure others do. After watching a fellow rider's headset freeze up one REALLY cold winter's night ride, I picked this up in hopes of keeping mine moving by keeping water/dirt/grime out. While my headset never froze up or had any issues on cold weather rides, I'm honestly not sure if this product worked or not. Everything still feels fine, steering wise, so I can only assume it worked.
Really keeps any type of grit from getting into your lower headset assembly. It'll only fit 1 1/8in steerer tubes though.