Some coins are rare and valuable. Maybe you have some special change hanging out in your pocket as we speak. The only way to find out is to learn which coins are special.
Coin collecting is one activity where blemishes can be a good thing. See a typo or malformation on your money? It could be worth something. Collectors love to buy the mint’s mistakes. Here are some sites to get you started:
Blifaloo illustrates and describes rare coins you may come across.
U.S. Coin Values Advisor and Coin Buying Advice give coin buying and selling tips.
The Fun Times Guide lists rare pennies.