oVirt is an open source alternative to VMware vSphere and provides an awesome KVM management interface for multi-node virtualization
Proxmox Virtual Environment --http://www.proxmox.com
Proxmox provides an open source server virtualization management solution supporting both KVM and container-virtualization. Proxmox also offers the reliable antispam and antivirus solution Proxmox Mail Gateway for high protection of email servers. Proxmox customers are found around the globe in businesses regardless of size, sector or industry as well as in NGOs and in the educational sector.
Optimize your infrastructure with VMware virtualization. From data center to lab, VMware virtualization consolidates servers, optimizes the software lifecycle, and provides business continuity via virtual machine, virtual server, and virtual pc solutions.