It's not just poor countries that use child labor, child labor is still used illegally and sometimes even legally in the US. Largely in agriculture.
Sadly these children miss out on a childhood, education, health care, and are often working in very unsafe an environment. One way you can help end child labor is to buy certified Fair Trade products. Also sharing this information with others can help as many don't know this is going on, especially in the US. If a company you like doesn't use Fair Trade products and ingredients contact them about making the switch. Together we can end child labor.