There is a significantly updated version of virt-top now available. On systems which support it, you can show the mapping of domains to physical CPUs and the amount of each physical CPU being used.
Screenshots: http://et.redhat.com/~rjones/virt-top/screenshots.html
There are also binaries available to download for i386 and x86-64. (The binaries are just self-contained Linux executables, no extra files or dependencies are needed, except for libvirt.so).
Downloads: http://et.redhat.com/~rjones/virt-top/download.html
If you are a systems administrator, what do you think could be improved about virt-top? Try it out and let me have your suggestions ...
Rich.