CSA Cloud Controls Matrix, v. 1.1
The Cloud Security Alliance (CSA) has just released their Cloud Controls Matrix, version 1.1. According to the CSA website, "The Cloud Security Alliance Cloud Controls Matrix (CCM) is specifically designed to provide fundamental security principles to guide cloud vendors and to assist prospective cloud customers in assessing the overall security risk of a cloud provider."
For somewhat sophisticated security professionals, the Matrix is a good starting point for a security assessment framework.
The tool can be found here: https://cloudsecurityalliance.org/research/projects/cloud-controls-matrix-ccm/