Take a look at the Au Pair in America site. You are required to have recent childcare experience and a full clean driving licence. The minimum length of commitment is 12 months. However, it is the most popular and thus serves as a good starting point. Through this organization, young people from all over the world are able to spend their summer helping out on a summer camp.
Various jobs are avilable.
These range from working in the kitchens to taking care of the children. Any nationality is able to apply so long as they are able to speak English and can attend an interview in a country in which CA has interviewers. Look at the following list of NGO's to get more ideas. Do be sure to check what you are required to pay in the way of fees and whether you will receive accomodation and food. Programs vary greatly.