We operate and manage several cloud infrastructure services both for ourselves and several client enterprises. Using several solutions for the management and deployment of virtualized resources, including VMware, Xenserver, and OpenStack, our Goto solution that we use internally is CloudStack.
CloudStack not only integrates well with the various forward facing customer billing and management solutions we use such as WHMCS, HostBill, and Blesta, but can manage virtualized resources directly and even works well sitting atop and management vSphere, vCloud Director, etc., and Xenserver - so many of the layers that only manage services under a particular virtualization technology can still be used directly or managed by CloudStack.
We highly recommend CloudStack as a solution for the management of enterprise resources in the cloud and use it everyday ourselves. Review collected by and hosted on G2.com.