Woo-hoo! I'm in the RC1 release for Windows Home Server.
It's kind of like a SAN (storage area network). For at home. Added hard drives donate their space to the pool. If there are two or more hard drives involved, duplication can be enabled.
Plus more: centralized backup, file sharing, printer sharing, remote admin, remote access to PCs, health monitoring, media streaming, etc.
Over the past few years I've been unsatisfied with the various network devices I've implemented at home for backups and shared files. I LOVE the idea of an easily configurable server that is expandable and that provides a central administration point for all the home network chores.
Yeah, I could have knocked something like WHS together myself, but I'm lazy and I have limited time. The wife already rolls her eyes and tells me I'm not allowed more than 6 hours of computer love on a weekend.
To sign up for RC1, get on over to http://connect.microsoft.com/WindowsHomeServer real quick.