FreeNAS: The Free NAS Server

FreeNAS is a free NAS (Network-Attached Storage) server, supporting: CIFS (samba), FTP, NFS protocols, Software RAID (0,1,5) with a Full WEB configuration interface. FreeNAS takes less than 16MB once installed on Compact Flash, hard drive or USB key.

This looks like NASLITE which I discussed a long time ago and ran for about a year. This one's free (obviously) and offers many more options. It looks like it's worth checking out.