I purchased an accounting and manufacturing system two years ago to
help us in our manufacturing operation.  The integration and
implementation has been a bust and I am looking to sell the license to
the software.

The accounting software is MAS 90 and the manufacturing software that
can integrate into the accounting software is called Job Ops.

What avenues are there to sell, put a value on the used software and
is it legal to sell the used software?  Any links to informative sites
would be appreciated.

This is just a free comment.  Only an official G-A Researcher with a
blue name can post an "answer" to your question.

Till then, this site and links maybe of interest to you:
http://en.wikipedia.org/wiki/Copyright_infringement_of_software

In general, if you purchased a copy of a software title, you are free
to sell it to someone else (as long as you don't keep a copy for
yourself).  Selling a "licence" sounds more complicated, you might
want to start by reading the purchase agreement that I'm sure you
signed when buying the license.  It probably spells out what you can
and cannot do.

Value is another issue.  I'm not familiar with the software you are
describing, but typically most people are only interested in quite
recent programs, and the value of older software quickly drops to
about zero.

before u selling the software, make sure that reading the license
agreenment of the software which u have 2 years later...

then u can proceed...na.. other wise it makes risk to you