This is a really simple trick to clean the faucet head that I found on a ton of blogs/websites.
1/3 Cup of Baking Soda
1 Cup Vinegar
Zip Lock Bag
Rubber band or Clip
Put the baking soda in the zip log bag. Then, SLOWLY, add the vinegar. Do this over the sink since it will bubble up (remember 3rd grade science). Pull the faucet out and dip in the bag. Use the rubber band or clip to hold the bag on the faucet head. Make sure the faucet head is fully submerged in the liquid. Wait about 1 hour then use a old tooth brush to scrub off all the yucky gunk.