Server and Client software to interoperate with Windows machines
http://www.samba.org/

Samba is the suite of programs by which a lot of PC-related machines
share files, printers, and other information (such as lists of
available files and printers). The Windows NT, OS/2, and Linux
operating systems support this natively, and add-on packages can
enable the same thing for DOS, Windows, VMS, UNIX of all kinds, MVS,
and more. This package provides an SMB/CIFS server that can be used to
provide network services to SMB/CIFS clients.
Samba uses NetBIOS over TCP/IP (NetBT) protocols and does NOT
need the NetBEUI (Microsoft Raw NetBIOS frame) protocol.