There is no specific example from the APA manual on citing websites of organizations and associations.
However, when you want to cite a whole website and there is no specific author or page number, you can use the following format suggested by the APA website:
All information and page number references are based on the 6th edition of the Publication Manual of the American Psychological Association (2009/10).
Need a copy of the Publication Manual? Click here for details. See Also: APA Style Guide to Electronic References, Sixth Edition