http://www.helmets.org/little1s.htm
This article is a part of the frequently updated and extremely helpful Bicycle Helmet Safety Institute website. It tells you all you need to know about riding with a young child on your bike, including when to start riding with baby it is recommended to wait at least a year) and information about carriers, trailers and sidecars. The site also has lots of safety information, tips on how to buy helmets, statistics and laws related to helmet-wearing and several links to other sites. Particularly handy is the list of helmet recall actions that goes back as far as 1995.