learning materials kvm/qemu/libvirt

I am doing a 2 year retraining at the moment to become a system admin. There are 2 weeks of HyperV on the schedule (sadly the only virtualization that will be taught in that course) in august and plan to sneak out of class during that time to to something useful and get a grip on the kvm/qemu/libvirt side of the VM cake (class is completely online, so the sneaking out is doable). Can anybody recommend good online learning resources for someone with yet quite foggy basic understanding of things? thanks and best Gunnar