"Pinyin is a system for writing the Chinese language in the Latin
alphabet. It is used throughout the world, including by the United States
government and by the news media.... The use of pinyin romanization by
libraries should also facilitate the exchange of data with libraries internationally."
- Library of Congress
A long-standing and comprehensive site of information on learning Chinese
developed and maintained by Carlos McEvilly. You may find it very useful
if you are interested in sinology and the Chinese language. You can even
learn Chinese on the Web with audio aid.
I have updated it adding a "Parenting" category for adoptive
parents per their request. A search engine is added to facilitate your
search. The site does not cover everything, therefore, your feedback is
very important to improve and add to it.