OS List

(POSIX)
UNIX (AT&T -> Novell -> SCO)
  [UFS]
  BSD (Berkeley)
    FreeBSD (Core team)
    NetBSD
      OpenBSD (Security)
    Mac OS X (Apple) 
      [Journaled HFS+, ZFS]
  Solaris (SUN) SunOS
    [ZFS]
  AIX (IBM)
  HPUX (HP)
  IRIX (SGI) 

Linux (GNU) (LSB FHS)
  [ext2,ext3,ext4,swap]
  Android (Google)
  Chrome OS (Google)

Windows (Microsoft)
  [FAT16, FAT32, NTFS]