I am playing with my newest toy, Windows Home Server (WHS), and I must say that this is by far the niftiest "little" piece of home software I have had my hands on (I may review it later - but if you don't know it then download the trial version and install, find your add-ins here and especially look at the Webguide for Windows Home Server and the Avast Professional Family Pack, which includes a WHS add-in).
To save power and space I have setup a portable computer with an external harddrive and now I was surfing around to find out how power management works with WHS.
There where different more or less clever solutions from shutting down at midnight and then using a timer device to turn it on again to more advanced solutions, but by far the best solution I found is using the built-in features of Windows Server 2003 together with a portable computer (In my Case a Dell D830 with 3 GB RAM, Core 2 Duo and 160 GB 7200 RPM disks).
These built-in features are explained and detailed in the whitepaper How to Enable Processor Power Management in Windows Server 2003 and applies of course to all server versions (I have used it before on my Shuttle that I use for Virtual Server labs with standard Windows Server 2003).
Another add-in I used was Marcel Nouwens free AutoExit 2008 for Windows Home Server that can do Wake-On-Lan (Perfect for my Shuttle) and handle remote shutdown, reboots, send messages or even open a Remote Desktop session) - so now I almost have my perfect home network / WHS solution running (I'm still awaiting a few add-ins so I can remotely stream MCE recorded TV (Should release in late January) and a add-in for total Desktop Management, I need my 802.11n to run better and the list continues endlessly ;-)