Below are two dial plan presentations from Cisco Live 2009.  Someone who recently passed the CCIE Voice recommended these as a reference.

EnterpriseDialPlanfundamentalsBRKVVT2008_brkvvt2008

AdvancedDialPlanDesignforIPTelephonyNetworksBR_brkvvt3000

CCVPImplementingInternationalDialPlansUsingCis_brkcrt1962