APA style refers to the citation format established by the American Psychological Association. APA is the style preferred by most of the disciplines in the social sciences.
APA Style tutorial
Basic online tutorial by American Pyschological Association
APA style guide FAQ
by the American Psychological Association
APA Formatting and Style Guide
by the Online Writing Lab (OWL) at Purdue
Citation Fox APA
by University Libraries, University at Albany, State Universities of New York
Templates and examples are provided for many different resource types in books, journals, online and WWW sources as well as miscellaneous print and other media.