The APUS library provides access to the full, official versions of the Chicago Manual of Style and The Bluebook (NOTE: Full access to The Bluebook is limited, see this page for eligibility requirements and access details).
Of course, you are free to purchase your own copies of the APA, MLA, and Turabian style guides directly from their respective publishers or from the bookseller of your choice.
APA style guide (The Publication Manual of the American Psychological Association, 6th edition)
Available in print (hardcover, softcover, spiral bound, and softcover (Spanish).