As many have emphasized, Linux is exceptional in the server market. For consumers however, many do not realize servers can be very small scale and reduced to embedded devices. I’ve been working on a Linksys Network Storage Device for my home lan. Basically the device is a Linux server running on 133Mhz ARM Processor with 32MB of ram. However it comes with a 100Mbit network port and 2 individual USB2.0 ports. You can plug in harddrives or media devices into the USB ports and once you add it to your network you have a shared harddrive. Its a low power device which is very good alternative to building a full server doing the same work and much more affordable.
The folks at nslu2-linux.org have put together multiple extra software packages and guides on how to do much much more than just a file server. Some examples would be a Web server, Software Revision control (SVN), TV media recorder, iTunes music server, Windows Domain Controller, and the list goes on. My intended functions right now are a LAN DNS Server, basic webserver, revision control, NTP (network time server) on top of file serving. My idea is to relagate some functions I have on my computer and others on my network into 1 primary (low power) machine.
It’s not up and running yet. I found information to over clock the CPU to 266Mhz, and soder in a RS232 serial port so I can see booting information and access a command prompt. Lots to play with – more information when it’s all hooked up.