Capitalization Rules at GrammarBook
http://www.grammarbook.com/punctuation/capital.asp

Wikipedia: Capitalization
http://en.wikipedia.org/wiki/Capitalization

OWL - Purdue Online Writing Lab: Capitals
http://owl.english.purdue.edu/owl/resource/592/1/

Fact Monster: Capitalization
http://www.factmonster.com/ipka/A0771333.html

English Plus: Rules for Capitalization Contents
http://englishplus.com/grammar/captcont.htm

InfoPlease: Capitalization
http://www.infoplease.com/ipa/A0001601.html