American Psychological Association - APA Style
The official, central page for APA style.

APA Style Blog
A branch of the official APA website that contains a running blog of APA questions and answers. You can even ask a question specific to your topic and paper.

Purdue Online Writing Lab (OWL)
A popular APA formatting and style guide.

Walden University - APA Guide
A useful guide with videos and explanations of APA style.