I’ve been using qemu and libvirt to create and manage virtual machines under Linux. I’m using Virtual Machine Manager to graphically manage the machines. I’ve been really impressed with qemu + KVM performanace, and Virt-Manager provides a very nice and easy to use interface. There is just one thing lacking, in comparison to “traditional” desktop virtualization software (eg. Virtualbox): there is no pre-configured way to share files between the host and the guest.