While the APAstyle.org may direct you to purchase their latest edition, the following web sites offer the same information free of charge. I have used many of them at one point or another, and below I share some of the most helpful.
The OWL at Purdue: Free writing help 24/7
http://owl.english.purdue.edu/owl/resource/560/01/--This site is exhaustive, which is very good if you have some weird reference that cannot fit into the major categories. Scroll to the lower part of the site to view the index.