Pinyin (拼音 pīnyīn, literally "join (together) sounds") usually refers to Hanyu Pinyin (汉语拼音 Hànyǔ Pīnyīn or "Han language Pinyin").
Hanyu Pinyin is the romanisation method promulgated and popularized by the government of the People's Republic of China for Standard Mandarin, the most widely used dialect of the Chinese language.
Pinyin is now universal for People's Republic of China. It is also the most widely used method of romanization outside of PRC. For instance, it is used by the Government of Singapore, the United States Library of Congress, and the American Library Association.
Other romanization styles that have the name "pinyin" in them include Tongyong Pinyin? and Postal System Pinyin? (unrelated to the modern day Pinyin).
More information at http://en.wikipedia.org/wiki/Pinyin, http://pinyin.info/ and the pronounciation can be practised at http://www.courses.fas.harvard.edu/~pinyin/.
gimpf: Is Wade-Giles anywhere else but in Taiwan of China used anymore?
More information at Wade-Giles and/or http://en.wikipedia.org/wiki/Wade-Giles
TDerz For character search for Go books
http://zhongwen.com/zi.htm could be useful. If you know how to look up radicals, hanzi or Kanji - and you need to know on this site too - then a book could provide a faster result (if at hand). The website provides English-, pinyin-, Cantonese, stroke number- and character-look-up.
Chinese pronunciation tool
Chinese Romanization Converter
Zhuyin Fuhao to Hanyu Pinyin converter and reverse