I read in a book : 8 weird things some cats eat or lick:

1. your face or hair - your moisturizer, cosmetics, or shampoo could come from by-products of slaughtered farm animals. Change your brand, or wash your face or hair in a little lemon juice or vinegar.
2. stamps - cats can be attraacted to the glue, which may contain remdered animal parts.
3. photographs - chemicals used in the processing of film could be attractive to your cat. Like stamps, there probably aren't enough noxious products on the photos to harm your cat, unless you're a professional photographer.
4. dirt - If there's not medical problem causing your cat to eat dirt, just make sure the soil - whether from your garden or your houseplants - doesn't contain pesticides, fertilizers, or chemicals.
5. concrete, metal, and other weird things
6. crossword puzzles (newspapers or letters) - the ink from the pen could be attracting your cat.
7. olives - experts believe its the preservatives in the jar that attracts the cat - plus the fact that some cats like food they can bat around before eating.
8. ice cubes - the texture and the temperature also seem to make ice cubes a popular item fro cats to eat and play with.