Howto Forge has a great howto for installing and configuring FreeNAS 0.68.
This tutorial shows how you can set up a network-attached storage server with FreeNAS. FreeNAS is based on the FreeBSD operating system and supports CIFS (samba), FTP, NFS, RSYNC, SSH, local user authentication, and software RAID (0, 1, 5). It comes with a powerful web interface and uses very little space on the hard drive – about 32MB.