This site is now out-of-date. It was based on FreeNAS 7. It has been left active here in case some of the information proves useful for those using the new NAS4Free. Wherever FreeNAS is referred to, consider replacing with NAS4Free.
FreeNAS is a free home server software. It is a good alternative to Windows Home Server, although no pre-configured hardware is available for it.
It is based on FreeBSD, which has its foundations in UNIX. However, this does not matter, since there is no need to understand any UNIX commands.
This wiki will guide you through the creation of a complete home server, using any i386 (i.e. basic PC) that can boot from USB Flash drives, and a USB drive (size 128MB-2GB). I recommend at least 128MB RAM, although 256-512MB may be necessary to take advantage of some of the more advanced features (which are not detailed here). A monitor and keyboard are only required for the initial installation (although it is possible to do this without a monitor), so you could just borrow them.
Sometimes the difficulty is in having too many options. So, I'm going to limit instructions to what most home users will require.
Just follow the menus across the top, from left to right, and top to bottom, and you should have a fully-featured home server by the end. Don't be intimidated by the number of steps, it really is very easy.