Samba - opening windows to a wider world.
Samba makes it possible for Windows users to connect to a Linux file-server. It is transparent for the user that it actually is a Linux file-server he/she is connected to.
Most Linux distributions can read and write to Windows file formats(FAT, FAT-32, NTFS). And Linux distributions can read and write to the Mac OS X file system HFS+. Thus also in regards to file system compatibility Linux is the most open and flexible operating system.