The official study guide is located here: http://www.arubanetworks.com/pdf/education/SG_ACSP.pdf.
As for study materials; hands on experience and attending the ACSP training class are going to be your biggest help. In addition, the Validated Reference Designs (VRDs) on the Aruba web site will also help you prepare; specifically the Mobility Controller v8, 802.11n v8, Campus Design v8, High Density...etc..