Red Hats’ standalone Enterprise Virtualization hypervisor based on KVM called Red Hat Enterprise Virtualization (RHEV) is moved into beta alonwith the tools to manage it for servers and desktops. The RHEV hypervisor is being designed to span up to 96 cores and 1 TB of main memory, which is the largest "Dunnington" Xeon 7400 box that Intel and its server partners can put into the field today and which is as large as next year's "Nehalem EX" Xeon 7500 servers are expected to span. The KVM hypervisor from Red Hat will be able to make a single partition span as many as 16 processor cores and up to 64 GB of main memory, which is double the CPU scalability of VMware's ESX Server 4.0 hypervisor. It can only span up to eight cores, but it can put 255 GB of memory on a single VM (That's not a typo. It is really 255 GB).
More info: The Register