slkvm is an application to provide some system tools to work with clustering and virtualization. It focuses on depending on as few external tools as possible but to also support as many virtualization technologies as possible. It works in a cluster environment where heartbeat runs virtual machines of nodes that have failed. It builds an "unheaded" cluster to avoid having a clear point of failure. It is able to build a two node cluster with everything redundant. It avoids compiling a new kernel or newer version of applications, so you can benefit from Debian security updates.
libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. You can use this for viewing and editing files inside guests, scripting changes to VMs, monitoring disk used/free statistics, P2V, V2V, performing partial backups, cloning VMs, and much more. libguestfs can access nearly any type of filesystem including: all known types of Linux filesystem (ext2/3/4, XFS, btrfs, etc.), any Windows filesystem (VFAT and NTFS), any Mac OS X and BSD filesystems, LVM2 volumes, MBR and GPT disk partitions, raw disks, qcow2, CD and DVD ISO images, SD cards, and dozens more. libguestfs doesn't need root permissions.
kvm-simple-init can perform the following actions on a KVM machine: start, stop, kill, and restart. It focuses on simplicity, and is fully implemented in just a few hundred lines of shell script. It is intended for people who do not want to run libvirt just for running a few VMs, or people who prefer to manage flat configuration files using their preferred configuration management system. It does not provide complicated configuration file format or parameters. Only two pieces of information are needed: a QEMU monitor port for the machine and the full KVM command line needed to start the machine (gives full configuration freedom). kvm-simple-init can be used directly as a system init script for starting all KVM machines on a host machine. Just drop it in /etc/init.d, and enable it with the tools provided by your UNIX distribution. kvm-simple-init was inspired by the init script of FreeBSD jails.
Xvisor is a type-1 hypervisor that aims to provide a monolithic, light-weight, portable, and flexible virtualization solution for ARMv5, ARMv6, ARMv7a, ARMv7a-ve, ARMv8a, x86_64, and other CPU architectures. It primarily supports full virtualization, and hence supports a wide range of unmodified guest operating systems. Paravirtualization is optional and is supported in an architecture independent manner (such as VirtIO PCI/MMIO devices) to ensure that no changes are required in the guest OS.