I've wanted a file server, but I don't feel like forking over the cash for a pre-built NAS. I was browsing Anandtech and read an article on file servers/NAS, and found out about FreeNAS. Even if you've never used a *nix OS before, you can easily install this. I'm using it with a Jetway mini-ITX board running an 800MHz VIA C3 and 256MB of DDR. I'd like to add a larger hard drive down the road, but for right now, it's been a very easy OS to administer. It just works and might be a good option for systems that might be seen as only a router (which was its previous job with my dad).