What are some alternatives?
When comparing Archipel and OpenNebula, you can also consider the following products
Proxmox Virtual Environment - Proxmox VE is an open-source server virtualization platform to manage KVM virtual machines, LXC, software-defined storage and networking, HA clustering, and multiple other out-of-the-box tools on a single solution.
OpenStack - OpenStack software controls large pools of compute, storage, and networking resources throughout a datacenter, managed through a dashboard or via the OpenStack API.
Virtualizor - Virtualizor is a powerful web based VPS Control Panel.
VMmanager - VMmanager is a virtualization management software, which presents a perfect tool for creating virtual machines, providing VPS services and building cloud infrastructure.
oVirt - oVirt is a virtualization management application.
Apache CloudStack - CloudStack is an open source cloud computing software for creating, managing, and deploying infrastructure cloud services.