The Open Group holds the UNIX trademark in trust for the industry, and manages the UNIX trademark licensing program.
UNIX and Linux Forums - Learn UNIX, UNIX commands, Linux, Operating Systems, System Administration, Programming, Shell, Shell Scripts
AIX - AIX is IBM's industry-leading UNIX operating system that meets the demands of applications that businesses rely upon in today's marketplace.
Lengthy encyclopedia-quality article from Bell Labs, covering the early days to the present versions.
Ordering page for the Open Group's Single Unix Specification.