Note: Please see Modules, which is now our preferred method of providing locally-built software to the Institute, as well as its various labs and centers.
/opt/local is managed via a Stow system.
If you are looking for a specific piece of software you can list the directory /opt/local/stow. Some software is linked in with the stow command directly into bin,lib,man,sbin directories in /opt/local.
This only pertains to RHEL6 and above. The software previously was found in /usr/local.