Xen takes GC up a level. It is a open source virtualization softwatre that allows you to run many different servers on a single piece of hardware. There are other packages out there - VMWare, for instance - but this one happens to be free. I love this quote from the site:
"Our grandchildren will say, 'I can't believe you used to run computers that weren't virtualized,'" predicts Margaret Lewis, commercial software strategist with AMD. Both AMD and Intel have built virtualization hooks that help Xen and other virtualization software run efficiently on their new dual-core chips that will start appearing in servers in 2006.
This can only get better and better. How many servers can you cram onto a single box? I know a lot of sysadmins like to run one application per server, but with Xen you can still do this and save computing resources. No Windows yet, it seems, but they will cave. They will have to, it's the future, now.