The 62-page document on the link below (current as of Aug. 2012) is one that I've been using on a regular basis for the past couple of years. It has helped me determine what facilities to visit this summer when I embark on a solo trip to 54 zoos/aquariums in 20 days. A new record! Many of the establishments are fairly small and that is why visiting 3 zoos per day is not an issue. Feel free to use this wonderful resource:
http://www.zoology.msu.edu/uploads/documents/nonAZAaccredited2012.pdf
http://www.zoology.msu.edu/uploads/documents/nonAZAaccredited2012.pdf